Dissertations / Theses: 'Anisotropy of magnetic susceptibility'

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Wang, Eric. "Anisotropy of Magnetic Susceptibility Investigation of the Coyote Mountain Shear Zone." Thesis, University of Louisiana at Lafayette, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10681403.

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The goal of this thesis is to test if the strain gradient preserved across the Coyote Mountain detachment shear zone can be correlated to change in the AMS fabric. Samples of granite mylonite derived from the Pan Tak granite were collected on a south-north transect across the Coyote Mountain shear zone, from lower structural levels up to the Ajo Road décollement. Evidence in the field shows an increasing degree of strain preserved in the mylonite, expressed by increasingly penetrative foliation and lineation with higher structural level toward the top of the shear zone. Strain was evaluated in the collected samples by application of the R_f/&PHgr; method. Results were then compared to anisotropy of magnetic susceptibility measurements in order to test whether magnetic fabric can be used as a reliable proxy for finite strain.

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Fanjat, Grégory. "Les fluctuations du champ magnétique terrestre : des variations séculaires récentes aux renversements." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20154/document.

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Le champ magnétique terrestre présente une vaste gamme de variations temporelles, de l'année à plusieurs millions d'années. J'ai étudié au cours de ma thèse divers aspects de ces fluctuations, des variations séculaires récentes aux renversements.La première partie de ma thèse porte sur l'archéomagnétisme, discipline qui permet de retracer l'évolution temporelle du champ magnétique terrestre au cours des derniers millénaires, principalement à partir des matériaux archéologiques. J'ai étudié deux jeux d'échantillons provenant pour l'un de la Grèce (période néolithique, 6800-3200 avant J.C.) et pour l'autre du Mexique (Palenque, période Maya Classique 320-840 après J.C.), dans le but d'acquérir de nouvelles données d'archéointensité et de mieux contraindre la variation séculaire du champ magnétique terrestre. La comparaison de mes données avec celles disponibles dans la bibliographie et avec les différents modèles globaux et régionaux a mis en évidence que les variations séculaires au Néolithique en Grèce et au cours du premier millénaire en Amérique Centrale sont très mal définies. Mes données suggèrent que des composantes locales, non prisent en compte dans les modèles globaux peuvent exister au niveau ces régions. Elles renforcent l'intérêt de développer des modèles régionaux précis, qui nécessitent un développement en harmoniques sphériques à un degré plus élevé. Pour ce faire, l'acquisition de nouvelles données de haute qualité est un élément majeur.La deuxième partie traite de la description d'un renversement du champ magnétique terrestre. Cette étude a été basée sur deux points précis: étudier les directions transitionnelles afin d'apporter de nouvelles contraintes sur le possible confinement longitudinal des pôles géomagnétiques virtuels (PGV) d'une part, et d'autre part vérifier des paléointensités transitionnelles obtenues sur la séquence volcanique d'Akaroa (Nouvelle Zélande), dont l'intensité est significativement supérieure à celles des intensités avant et après le renversement. Nous avons ré-échantillonné cette séquence, et l'évolution directionnelle obtenue pour ce renversement est une succession complexe de polarités N-T-R-T-N-T-R. Les PGV obtenus semblent se regrouper sous deux bandes longitudinales sous l'Australie et l'Amérique, ce qui renforce l'hypothèse d'une interaction entre le manteau et le noyau sur plusieurs millions d'années. Suite à une étude de minéralogie magnétique, j'ai sélectionné les échantillons susceptibles de fournir une valeur de paléointensité par les méthodes de Thellier et du multispecimen. Les paléointensités obtenues sont relativement faibles (environ 20 microT) au cours du changement de polarité et forte à la fin de la séquence. Mon interprétation, basée à la fois sur les valeurs de l'intensité du champ et sur les données radiochronologiques montrant que la séquence s'est mise en place très rapidement, est de considérer que seul le renversement C4Ar.1n-C4Ar.1r a été enregistré dans cette séquence. Dans cette hypothèse, le renversement montre un cheminement complexe comparable à d'autres renversements enregistrés dans l'hémisphère nord (Steens Mountain par exemple), incluant un phénomène de rebond avant de se stabiliser. La troisième partie de ma thèse est consacrée au développement d'une nouvelle méthodologie et d'un nouvel appareillage pour déterminer des paléointensités. Le faible taux de réussite des expériences de paléointensité de l'étude précédente m'a poussé à m'intéresser au protocole multispecimen, qui peut s'appliquer aux échantillons possédant un comportement polydomaine. L'inconvénient technique majeur de cette méthode réside dans l'application du champ le long de l'aimantation naturelle, difficile à réaliser avec précision dans les fours standards. Pour ce faire, nous avons décidé de développer des porte-échantillons permettant d'orienter les échantillons dans l'espace pour le four standard et un prototype de four à chauffage ultra-rapide particulièrement bie
The Earth's magnetic field shows a large range of temporal variations from the year to several million years. I studied during my PhD thesis several aspects of these fluctuations, from recent secular variations to reversals.The first part of my manuscript deals with archeomagnetism, a discipline that allows to track the temporal variations of the Earth's magnetic field through millennia, mainly from archeological materials. I studied two sets of samples, one from Greece (Neolithic period 6800-3200 B.C.) and the other from Mexico (Palenque, Maya Classic period 320-840 A.D.), to acquire new archeointensity data in order to better constrain the secular variation of the geomagnetic field. By comparing my data with those available in the literature and with the various global and regional models, I showed that the secular variations during the Neolithic in Greece and during the first millennium in Central America are poorly defined. My data suggest that local components, not described by global models, may exist in these regions. They reinforce the importance of developing specific regional models, which require development in higher spherical harmonic degree. As a consequence, the acquisition of new high quality data is of main importance. The second part presents the description of a geomagnetic field reversal. This work was based on two points: first by studying transitional directions to provide new constraints on the possible preferred longitudinal paths of virtual geomagnetic poles (VGPs) and second by checking transitional paleointensities obtained on a volcanic sequence in Akaroa volcano (New Zealand). Indeed the transitional field intensity is significantly higher than the field intensity before and after the reversal. We re-sampled this sequence, and the directional results show a complex sequence of N-T-R-T-N-T-R polarity. The transitional VGPs obtained are clustered in two longitudinal bands through Australia and America. This observation seems to reinforce the assumption of a core-mantle interaction over several million years. Following a rock magnetic study, I selected samples that could provide a value for the Thellier and multispecimen paleointensity methods. The obtained paleointensity are relatively low (about 20 microT) during the polarity change and strong at the end of the sequence.Based both on the field strength values and on the radiochronological ages, showing that the sequence was erupted in a very short time, I suggest that only the C4Ar.1n-C4Ar.1r reversal was recorded in this sequence. In this assumption, the reversal shows a complex path comparable to other reversals recorded in the northern hemisphere (for example the Steens Mountain), including a rebound before stabilizing.Finally the last part is devoted to the development of a new methodology and a new apparatus to determine absolute paleointensity. Following the low success rate of paleointensity experiments from the previous study, I decided to test the multispecimen protocol, which can be applied to samples yielding a predominant multidomaine behavior. The main technical drawback of this method lies in the application of the laboratory field along the natural remanent magnetization, a difficult task to perform accurately in standard paleointensity ovens. Thus, we decided to adapt sample holders from our standard oven in order to allow the sample orientation in space and to develop an ultra-fast heating oven prototype particularly well-suited for this method, allowing to apply the laboratory field in the 3 dimensions. I checked the different multispecimen protocols on historical lavas from Reunion and Etna volcano, yielding very different magnetic mineralogies. For all flows, I obtained paleointensities very close from the expected values, regardless from the magnetic mineralogy, revealing the feasibility of our apparatus and the promising interest of the method. The application of various corrections on the statistical estimation o

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Hernandez, Brett M. "Physical Volcanology, Kinematics, Paleomagnetism, and Anisotropy of Magnetic Susceptibility of the Nathrop Volcanics, Colorado." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1400251995.

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Bjork, Andreas. "Characterizing magnetic susceptibility and remanent magnetization of magnetite and hematite rich drill-core samples at Blötberget." Thesis, Uppsala universitet, Geofysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-347975.

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Laboratory magnetic measurements are used to develop a methodology to characterize the Kiruna-type Rare Earth Elements (REE) bearing apatite iron-oxide deposits at Blötberget in central Sweden. This high-grade ore deposit is known to have sharp boundaries between lens shaped main ore bodies of magnetite-rich ore, and a complex hematite-rich ore associated with pegmatites and skarn formation. The thesis covers laboratory magnetic measurements of 37 samples originating from eight drill cores and reference samples from previously mined area. It focuses on on-covering how the samples relate in terms of magnetic susceptibility, further its dependency on temperature, frequency, field and the orientation. The results are correlated with petrographic analysis previously performed on accompanying thin sections. The measurements show that magnetite with strong susceptibility contribution overshadow the hematite contribution in the samples. Transition changes in susceptibility are noticeable when crossing the Verwey temperature; -153°C, Curie temperature; 580°C and Néel temperature; 680°C. The Morin temperature appears at -60°C, or is missing. Linear relationships are identified between the magnitude difference in susceptibilities across transitions at high temperature and wt% magnetite and hematite have been identified. The Blötberget skarn and hematite-rich ore samples have a higher degree of susceptibility anisotropy than the other ore-types. Blötberget samples are dominated by multidomain characteristics in remanence, saturation and coercivity. High temperature measurements have shown that the magnetite is close to pure. The low temperature measurements suggest hematite is impure or bears a petrological footprint. The study also shows that rich iron ore samples sometimes can be at risk of being overlooked with standard methods of measuring susceptibility
Laboratorietekniska metoder kan användas som ett komplement till malmgeologi och geofysisk prospektering. I denna metodstudie karaktäriseras apatitjärnmalm från Blötberget, nära Grängesberg. En fyndighet bestående av linsformade malmkroppar rika på magnetit och ofta avskilda men komplexa hematitrika stråk. Studien är gjord 37 prover från totalt 8 borrkärnor, och lokaler som tillhörde produktion från gruvverksamhet under 1900-talet. Mätmetoderna fokuserar på att kartlägga malmens magnetiska egenskaper, och hur temperatur, frekvens, fältstyrka samt riktning påverkar dessa. Resultaten jämfördes med tidigare petrografisk studie av tillhörande tunnslip Resultaten visar att magnetit står för merparten av susceptibiliteten i proverna, men att även hematit kan urskiljas och kvantifieras. Temperaturberoende har påvisats vid övergångar för Verwey-temperatur; -153°C, Curie-temperatur; 580 °C, och Néeltemperatur; 680 °C. Den förväntade Morin-temperaturen vid -14°C, påträffades vid -60 °C eller saknas helt för flera av de hematitrika proverna. Magnetiskt anisotropa prover återfinns bland prover som identifierats som skarn eller hematitrika. Magnetisk granulometri visar karaktär av multidomäntyp med låg magnetisk coercivitet och hög satureringsförmåga. Högtemperaturmätningar av susceptibilitet visar på ren magnetit för prover från Blötberget. Samtidigt visar lågtemperaturemätningar att hematit sannolikt har inblandning av titanium eller bär på ett mer komplext förflutet. Studien visar också att det finns en risk i att enbart förlita sig på bulksusceptibilitet för prover rika på malm.

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Trutner, Sarah D. "An Investigation of AMS in Oman Ophiolite Gabbros." Oberlin College Honors Theses / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1470493515.

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Seaux, Gage E. "Analog Modeling of Anisotropy of Magnetic Susceptibility as Affected by Pure Shear Strain on Original Magnetic Fabrics of Sedimentary Rocks." Thesis, University of Louisiana at Lafayette, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10683064.

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Analysis of the anisotropy of magnetic susceptibility (AMS) is an easy, non-destructive method to determine the preferred orientations of minerals in rocks and rock analogs. The orientations of the principal susceptibility axes (K_max≥K_int≥K_min) of the AMS ellipsoid are generally parallel to the principal axes of the strain ellipsoid (X≥Y≥Z). The orientations of the AMS axes as well as the magnitudes change in response to strain, though a generally accepted correlation between the magnitudes of the principal axes of AMS and strain has not yet been established. A successful correlation of the magnitudes of the principal susceptibility axes of AMS and strain would allow an easy and non-destructive method of quantitative strain analysis. This would also allow quantitative strain analyses of rocks where traditional methods using strain markers fail. In this study, the quantitative aspect of the relationship between strain and AMS is investigated experimentally using artificial mineral mixtures with a sedimentary initial magnetic fabric in an attempt to correlate strain to AMS. Mineral mixtures of magnetite, biotite, and specular hematite with a matrix of Art Time Dough^® (similar to Playdoh^®) were mixed separately. To create a random magnetic fabric, the samples were kneaded by hand for approximately 15 minutes. The samples were then strained to 70% strain in one direction to create a sedimentary initial magnetic fabric. The orientation of this strain became the Z axis of the strain ellipsoid. The samples were then strained perpendicular to this axis incrementally from 0% to 40% strain in 5% increments, with the AMS measured at each interval. The orientation of this strain became the Y axis of the strain ellipsoid. The data from these experiments resulted in the quantitative correlation of strain and AMS for the magnetite mineral mixtures. The biotite and specular hematite mixtures contain enough magnetite inclusions and magnetite conversion respectively to dominate the AMS. This creates a more complex relationship that is not easily correlated quantitatively to strain. The experiments demonstrate that a strong qualitative relationship exists between both the orientations and the magnitudes of the axes of the strain and AMS ellipsoids.

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Andersson, Magnus. "3D Structure and Emplacement of the Alnö Alkaline and Carbonatite Complex, Sweden : Integrated Geophysical and Physical Property Investigations." Doctoral thesis, Uppsala universitet, Geofysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-248113.

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Carbonatites are carbonate-rich magmatic rocks that are rare and of great relevance for our understanding of crustal and mantle processes. Although found on all continents and in settings ranging from Archaean to present-day, their deeper plumbing system is still poorly understood. Therefore, the main goal of this thesis is to broaden the existing knowledge of carbonatite systems, often limited to surface geological observations, by providing depth constraints using a number of geophysical methods and petrophysical measurements. The Alnö alkaline and carbonatite complex in central Sweden was chosen for this purpose. Data from three reflection seismic lines, ground gravity and magnetic measurements are presented. These data are complemented by a series of petrophysical measurements, including ultrasonic velocities, density, magnetic bulk susceptibility, anisotropy of magnetic susceptibility (AMS), and magnetic remanence, to aid in the interpretation of the geophysical data. The reflection seismic data indicate a solidified saucer-shaped fossil magma chamber at about 3 km depth. Caldera-style volcanism, constrained by surface geological observations, provides a plausible scenario to explain the emplacement of the complex, suggesting that carbonatite magmas have been stored, transported and erupted in a similar manner to known emplacement mechanisms for silicic calderas, although these are compositionally different. The AMS data from most of the carbonatite sheets in Alnö show a strong degree of anisotropy and oblate-shaped susceptibility ellipsoids. A set of syn- and post-emplacement processes that may control the AMS signature is evaluated based on the dataset. Overprinting of the primary flow patterns by processes related to sheet closure at the terminal stage of magma transport may explain the AMS observations. A complementary study using 3D inversion of ground gravity and aeromagnetic data was then carried out to better delineate the 3D internal architecture of the complex. Resulting models indicate a depth extent of the complex to about 3-4 km, consistent with the interpretation of the reflection seismic data. The modelling results of a ring-shaped magnetic anomaly observed in the Klingefjärden bay adjacent to Alnö Island further suggest that the complex may extend laterally about 3 km towards the north.

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Michlesen, Karen Joyce. "Heterogeneous internal fabric of the Mount Barcroft pluton, White Mountains, of eastern California: an anisotropy of magnetic susceptibility study." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9720.

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Anisotropy of magnetic susceptibility (AMS) have been used with great success for determining the internal structure and fabrics of Jurassic and Cretaceous plutons of felsic-intermediate compositions in the White-Inyo Range of eastern California. However, application of the AMS techniques to the Mount Barcroft pluton, located in the northern White Mountains, has yielded anomalous scalar and directional AMS data indicative of unprecedented heterogeneity on the meter-kilometer scale. The 165 Ma Mount Barcroft pluton is primarily of granodiorite composition and was intruded into the Barcroft Structural Break, a northeast striking, steeply dipping structure that juxtaposes Mesozoic metavolcanic rocks to the north against Proterozoic-Paleozoic metasedimentary rocks to the south. Two oriented hand samples (A and B) were collected at each of 78 sites distributed on a 1 kilometer grid pattern across the 5 by 15 kilometer Mount Barcroft pluton and oriented cores were prepared from these hand samples for AMS analysis. Microstructure identification of single thin sections prepared for each sample site yielded primarily magmatic with minor solid-state structures. A highly heterogeneous distribution of scalar parameters (Km, P%, F%, L%, T) was documented both between sample sites and between the A and B cores at individual sites. The heterogeneity may be the result of complex mineral assemblages and the interaction between different magnetic mineral species ranging from single domain to pseudo-single domain to multidomain magnetite. More problematic are the directional parameters between A and B cores in orientation and fabric type (e.g. prolate and oblate susceptibility ellipsoids) occur which cannot be readily explained by a complex mineral assemblage. Different fabric types in A and B cores at individual sample sites could be the result of discrete, temporally unrelated, magma pulses of variable composition and viscosity. Heterogeneity of scalar and directional AMS parameters in the Mount Barcroft pluton, and its contrast with the homogeneous AMS signatures within similar age plutons to the south, may provide evidence for a previously unrecognized magma source beneath the northern White Mountains.
Master of Science

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Ridier, Karl. "Etudes des relations magnéto-structurales dans les composés à base moléculaire par diffusion des neutrons : des molécules individuelles aux nanoparticules." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112312/document.

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Un des enjeux majeurs dans le domaine du magnétisme moléculaire est de mieux comprendre et prévoir, dans les composés à base moléculaire, les corrélations qui existent entre les propriétés structurales (modulables à partir de méthodes de synthèse de type « bottom-up ») et les propriétés magnétiques. En particulier, la compréhension et la maîtrise de l’anisotropie magnétique à l’échelle locale est primordiale, notamment en vue de concevoir des molécules-aimants avec de plus hautes températures de blocage. Dans ce contexte, ce travail de thèse s’organise autour de deux grands axes. La première partie se concentre sur la détermination et la caractérisation de l’anisotropie magnétique locale dans des complexes moléculaires d’ions de transition de faible nucléarité. La diffraction de neutrons polarisés (PND) nous a permis, pour la première fois, de mettre clairement en évidence le tenseur de susceptibilité magnétique locale dans un complexe moléculaire mononucléaire de Fe3+ Bas-Spin ainsi que dans deux complexes, mononucléaire et dinucléaire, de Co2+ Haut-Spin. Cette approche novatrice mène à l’établissement de relations magnéto-structurales claires et directes, en reliant les directions magnétiques locales propres à l’environnement de coordination des ions métalliques et en particulier aux axes locaux de distorsion. Nous avons également mené l’étude originale d’un complexe à transition de spin thermo-induite de Mn3+ par diffusion inélastique de neutrons (INS) dans les deux phases Haut-Spin (HS) et Bas-Spin (BS). Cette étude nous a conduits à la proposition d’un modèle d’hamiltonien de spin anisotrope dans les deux états HS et BS, en relation avec la structure du complexe. Dans une seconde partie plus exploratoire de la thèse, nous avons mené une étude complète des propriétés structurales et magnétiques de nanoparticules ferromagnétiques d’analogue du bleu de Prusse CsNiCr, par diffusion de neutrons aux petits angles (SANS). Les effets de taille, d’organisation et de concentration sur leurs propriétés superparamagnétiques ont ainsi été clairement mis en évidence. En particulier, nous avons mis en exergue, pour les particules de plus petite taille (5 nm de diamètre), une contribution magnétique qui résulte de la manifestation d’un phénomène collectif, tandis que celles de plus grande taille (28 nm de diamètre) apparaissent être dans un état complètement multidomaine
One of the major issues in the field of molecular magnetism is to better understand and predict the correlations between the structural properties of molecule-based compounds and their magnetic properties, all of which may be tunable using “bottom-up” synthesis methods. In particular, the understanding and control of the magnetic anisotropy at the atomic scale is essential, especially with the aim to design Single-Molecule Magnets (SMM) with higher blocking temperatures. In this context, this thesis work is focused on two mains subjects. The first part deals with the determination and the characterization of the local magnetic anisotropy in low-nuclearity molecular complexes based on transition ions. Polarised neutron diffraction (PND) allows us, for the first time, to directly access the local susceptibility tensor in a Low-Spin Fe3+ mononuclear complex as well as in two, mononuclear and dinuclear, High-Spin Co2+ complexes. This innovative approach leads to the establishment of unique and direct magneto-structural correlations, by relating the local magnetic principal directions with the coordination environment of the metallic ions and, in particular, with the local distortion axes. We have also carried out an original investigation by inelastic neutron scattering (INS) of a Mn3+ thermo-induced spin-transition compound in both High-Spin (HS) and Low-Spin (LS) states. On the basis of this study, we were able to propose an anisotropic spin-Hamiltonian model in both HS and LS phases, and their relationships with the structure of the molecule are discussed. In a second more exploratory part of the thesis, we have carried out by small-angle neutron scattering (SANS) a complete study of the structural and magnetic properties of Prussian blue analogues (PBA) ferromagnetic nanoparticles CsNiCr. The effects of size, organization and concentration on their superparamagnetic properties have been clearly highlighted. In particular, a strong magnetic contribution has been observed for the smallest particles (5 nm diameter) which results from the manifestation of a collective process, while the biggest (28 nm diameter) appear to be in a multi-domain state

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Humbert, Fabien. "Analyse pétrophysique et anisotropie de roches détritiques dans des systèmes compressifs en présence de failles actives : exemple des prismes de Taiwan et de Nankai." Thesis, Cergy-Pontoise, 2010. http://www.theses.fr/2010CERG0480/document.

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Analyse pétrophysique et anisotropie des roches détritiques dans des systèmes en compression et sous influence de failles actives : Exemple des prismes de Taiwan et du prisme de Nankai (Japon)L'objectif de cette thèse est l'étude de la déformation enregistrée par des roches d'origine détritique dans des domaines sujets au raccourcissement tectonique sub-horizontal (Layer Parallel Shortening) et à des failles actives. Cette étude est basée sur la caractérisation de diverses propriétés physiques et de leur anisotropie à l'échelle de l'échantillon dans le but de décrire à plus grande échelle la structure d'un prisme d'accrétion. Deux prismes ont ainsi été échantillonnés, le premier est le prisme inactif de Taiwan dans le cadre du projet TCDP et le second considéré comme actif celui de Nankai dans le cadre du projet NanTroSeiZE. La microstructure d'une roche sédimentaire, y compris en l'absence de déformation tectonique, présente toujours une ou plusieurs caractéristique(s) anisotrope(s) liée(s) à la forme, à l'orientation préférentielle ou à l'arrangement de ses éléments constitutifs. De nombreux travaux ont porté sur les conséquences de ces anisotropies sur les propriétés physiques, d'abord dans un but prédictif, puis selon une démarche inverse visant à caractériser, à l'aide de modèles, microstructures et histoire tectonique associée. Dans cette thèse la confrontation des résultats obtenus pour différentes propriétés physiques (principalement vitesses des ondes acoustiques, susceptibilité magnétique et aimantation rémanente) met en évidence des réponses sélectives liées à un fort contrôle de la lithologie.Au niveau de prisme de Taiwan, deux résultats majeurs ont été obtenus. D'une part, la comparaison des anisotropies magnétiques et acoustiques a permis de montrer une évolution différentielle de la déformation entre les roches riches en matrice (siltite) par et celles plus riches en grain sableux (grès). D'autre part, les résultats combinés de l'anisotropie des ondes P, l'étude microstructurale et la minéralogie magnétique, montrent un comportement particulier des échantillons situé dans le mur de la faille FZB1136, considérée comme responsables du séisme de Chi-Chi en 1999. Un réseau de structures dilatantes fortement perméable à permis la circulation de fluides, de néo-cristallisation de calcite et de néoformation de minéraux magnétique. Sur le prisme de Nankai, une estimation de la quantification de la déformation enregistrée par les échantillons du prisme est modélisée en utilisant le modèle de March et les paramètres de susceptibilité magnétique. Les différents travaux réalisés dans cette thèse mettent en évidence un couplage direct de certaines propriétés physiques mesurées avec certains effets de déformation, chaque propriété caractérisant un point précis de la fabrique enregistré dans les roches.Mots-clefs : Anisotropie, susceptibilité magnétique, vitesses d'ondes ultrasoniques, déformation, fabrique, microstructures, faille inverse, TCDP, NanTroSeiZE
Petrophysics of sedimentary rocks in compressive regime near active faults: examples of the Taiwan and Nankai accretionary prismsThe objective of this PhD is to study the deformation recorded by detrital rocks in areas subject to sub-horizontal tectonic shortening (Layer Parallel Shortening) and active faults. This study is based on the characterization of various physical properties and their anisotropy at sample scale in order to describe larger-scale structure of an accretionary prism. Two prisms have been sampled, the first is the inactive in Taiwan prism (TCDP project) and the second active the Nankai prism (NanTroSeiZE project).Sedimentary rocks microstructures, regardless of the degree to which they were loaded tectonically, always present some anisotropic characteristic emerging from a preferential shape, orientation or distribution of its constituents. Numerous studies have focused on the effect of such anisotropies on physical properties, first for prediction purposes, then to conversely get diffuse strain insight through the use of various effective medium models. In this thesis, the comparison between results obtained in discrete samples for various physical properties (essentially acoustic wave velocities, magnetic susceptibility and remanent magnetization) reveals selective responses due to a strong lithologic control.In TCDP, two significant results are reported. On the one hand, comparison of magnetic and acoustic anisotropy showed a differential evolution of deformation between the matrix-rich rocks (siltstones) and those with coarser granular fraction (sandstone). On the other hand, the combined results of the anisotropy of P waves velocity, microstructural analysis and magnetic mineralogy, show a peculiar behavior of the samples located in the wall of the fault FZB1136, considered to be responsible of the Chi-Chi earthquake in 1999. A network of highly permeable dilatant structures allowed the circulation of fluids, neo-crystallization of calcite and neoformation of magnetic minerals. On the Nankai prism, an estimate of quantifying the deformation recorded by the samples of the prism is modeled using a simple March-type model and the parameters of magnetic susceptibility. The various work in this thesis show a direct coupling of physical properties measured with some aspect of deformation, each property characterizing a specific point of the fabric recorded in rocks.Keywords : Anisotropy, magnetic susceptibility, ultrasonic wave velocity, strain, fabric, microstructures, thrust fault, TCDP, NanTroSeiZE

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Liodas, Nathaniel Thomas. "Gneiss dome development & transcurrent tectonics in the Archean: example of the Pukaskwa batholith and Hemlo shear zone, Superior Province, Canada." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/753.

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Archean greenstone belts typically form narrow sheared basins separating bulbous tonalo-trondjhemo-granodioritic (TTG) batholiths. The role played by gravity in the development of such dome-and-keel structures is a key question in Archean tectonics. The Pukaskwa batholith - Hemlo shear zone (HSZ) is a representative example of the dome-and-keel structures that are common in Archean terrains. This region has received considerable attention because the HSZ hosts several major gold deposits that are currently being mined. Late dextral strike-slip kinematics of the HSZ are well recorded by abundant strain markers in greenstone rocks, whereas the quartzofeldspathic coarse-grained rocks of the Pukaskwa batholith bear no macroscopically visible fabric. The goal of this study is to understand the structural history of this greenstone belt-batholith system. The Pukaskwa batholith is a heterogeneous assemblage of TTG gneisses bounded by the Hemlo greenstone belt to the north. The density of the Pukaskwa batholith rocks (density = 2700 kg/m3) is on average less than that of the Hemlo greenstone rocks (density = 3000 kg/m3). Since Archean geotherms were considered higher than modern equivalents, the effective viscosity of the TTG rocks might have been sufficiently low to allow their diapiric ascent through denser greenstone rocks. Alternatively, the emplacement of the TTG batholith might have been driven primarily by transpressive tectonics. The anisotropy of magnetic susceptibility (AMS) provides valuable information on the internal fabric of the Pukaskwa batholith. This study provides the kinematic information needed to support either the diapiric or the transpressive tectonic model. AMS recorded east-west trending prolate and plano-linear fabrics across the northern section along the contact, suggesting that transpressional forces from the Hemlo shear zone affected the emplacement of the Pukaskwa batholith. Away from the contact, fabrics are generally flattened, indicative of doming through diapiric processes. Also, in order to fully evaluate the diapiric hypothesis, it is necessary to obtain reliable data on rock densities across the Pukaskwa batholith. The density of about 360 representative specimens from the Pukaskwa batholith has been measured and will constitute a valuable database for future gravimetric investigations by mining companies. The significant degree of correlation between high-field magnetic susceptibility and density in the Pukaskwa batholith should be taken into account in geophysical exploration in Archean terrains, only as a proxy for iron content.

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Dall'Olio, E. "SEDIMENTOLOGICAL AND MAGNETIC ANISOTROPY ANALYSES ON PALEOCURRENT DIRECTIONS IN TURBIDITES FROM THE NORTHERN APENNINES (ITALY)." Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/169977.

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This PhD thesis focuses on the validation of an objective method to define paleocurrent directions in turbiditic systems: the anisotropy of magnetic susceptibility (AMS). The final purpose of this study is to calibrate paleocurrent directions estimated with this geophysical method to directions estimated from classic sedimentological indicators, and therefore verify the applicability of this method to cases where sedimentological paleocurrent indicators are absent such as in drill cores. Two selected turbiditic units outcropping in the northern Apennines, the Marnoso Arenacea Formation (Miocene, northern Apennines) and on the Castagnola Formation (Oligo-Miocene, Tertiary Piedmont Basin), were investigated. These basins have different depositional settings: the Marnoso Arenacea Formation filled a foredeep basin nearly 200 km long and 60 km wide, whereas the Castagnola Formation filled an episutural basin 6 km long and 4 km wide. AMS analyses were successfully applied to both formations on a total of 853 samples taken in a wide range of depositional intervals selected by means of detailed sedimentological analyses, and were successively cross-validated by direct estimates of flow directions from sedimentological indicators (ripple marks, flute marks, etc.). In the Marnoso Arenacea Formation, a robust correlation between magnetic fabric and paleocurrent directions obtained from sedimentological indicators was found in massive, parallel-laminated, and cross-laminated sandstones. These depositional intervals show well-clustered AMS data with an overall flow-aligned fabric. Instead, highly dispersed AMS fabrics are apparently common in convoluted and undulated sandstones as well as in debrites, suggesting depositional processes that partially prevented grains’ orientation (e.g., en masse freezing) or post-depositional processes that disrupted the original current-induced fabric (e.g., post-depositional dewatering). AMS fabrics typical of deposition in standing water was observed in the hemipelagites of the Castagnola Formation. Instead, in the fine-grained sediments of the Marnoso Arenacea Formation (White Marlstone beds), an AMS fabric interpreted as current-induced was observed and interpreted as due to muddy contourites. The study on the Castagnola Formation was carried out primarily to evaluate the effects of basin confinement on turbidity flow dynamics. In this small, confined turbidite system, we observed a strong correlation between magnetic fabric and bed-thickness distribution whereby beds thicker than ~1.20 m show high magnetic fabric variability and maximum susceptibility axes dispersion, whereas beds thinner than ~1.20 m show better developed magnetic fabrics with maximum susceptibility axes oriented consistently parallel to the mean paleoflow direction from flute casts. We believe that ~1.20 m represents a thickness threshold separating large flows that covered the entire basin floor interacting in a complex fashion with the basin’s margins from small volume flows that did not interact with the basin’s margins and produced better-defined flow-aligned AMS fabrics. Potential future developments of this thesis are: (1) deepening of our understanding on the relationships between grains’ orientations and magnetic minerals that contribute to the AMS signal by means of textural analyses, neutron diffraction and x-ray tomography. Preliminary results indicate that paramagnetic muscovite principally controls the observed current induced AMS fabric; (2) testing the AMS method on drill core samples, where flow marks (i.e., flute casts) are either absent or non-observable.

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Polat, Wiers Gülsinem. "Palaeomagnetism and Magnetic Fabrics of The Lake Natron Escarpment Volcano-sedimentary Sequence, Northern Tanzania." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-398409.

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The East African Rift System diverges in the Lake Natron Basin of Northern Tanzania and is a major zone of continental extension and crustal thinning with resulting in active tectonics and volcanism. The discovery of Acheulean technology in Olduvai Gorge and Peninj as well as the presence of significant volcanic centers, has made in the region subject to studies in various disciplines. However, lack of precise radiometric age constraints due to the complex geology of the region is a major drawback. The basin is bordered on the western side by an escarpment that contains thick sequences of volcanic (nephelinites, basanites, hawaiites, alkali basalts), volcaniclastic and lacustrine strata that predates 1.2 Ma. This thesis is based on 41 rock samples that were collected from two geological sections, the Endukai Kete (EK) and Waterfall (WF) sections and aims to establish a preliminary geomagnetic polarity time scale (GPTS) for the Natron Escarpment, together with establishing possible flow directions of the volcanic lavas within these sections. Nephelinites of EK section have an inferred NW-SE direction of flow, based on study of anisotropy of magnetic susceptibility. They record a normal polarity that most likely correspond to the Cobb Mountain Event (CMT; 1.187-1.208 Ma), although there is an 80-ka discrepancy between the CMT event and the dated lavas. The most probable source is the Mosonik that erupted nephelinitic lavas 1.28 Ma ago. The palagonitic tuff layer below the nephelinites displays reverse polarity and a NE-SW direction of flow. Due to the absence of approximately 200 m strata within the basanite series of the section, regional lithological correlation is used to constrain the GPTS pattern. Hajaro Beds of the Peninj Group to the north of the escarpment, postdates the Olduvai Event (1.71 to 1.86 Ma) and lacustrine strata of the escarpment for EK and WF sections are deposited over the same unconformity and share depositional similarities. Therefore, the lacustrine strata are correlative to Hajaro beds and the normal event observed within the basanite series of both sections is attributed to the Réunion Event (2.116 – 2.137 Ma). The establishment of a preliminary magnetostratigraphic sequence presented in this thesis demonstrate that the rift escarpment in northern Tanzania is suitable for paleomagnetic dating. Future studies should be conducted to establish a more detailed and constrained magnetostratigraphic section, which will be of great use in this part of the African Rift where radiometric dating has been challenging.

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Maher, Clare. "An investigation of depositional mechanisms of pyroclastic density currents using anisotropy of magnetic susceptibility (AMS) and a detailed stratigraphic study of the La Caleta Formation, Tenerife." Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/27725.

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This thesis describes La Caleta Formation and its eruptive history interpreted using sedimentary logs, isopach and isopleth data, granulometry and geochemical studies. The formation has been subdivided into six members, which were emplaced during five eruptive phases. The eruption commenced with fallout from a Plinian eruption column that collapsed, generating a rapid succession of short-lived pyroclastic density currents that deposited extensive ignimbrites and co-ignimbrite ash layers, culminating in a more sustained pyroclastic current that deposited a thick, predominantly massive ignimbrite, capped with a lithic breccia interpreted to represent caldera collapse. Fine ash layers can be deposited by ashfall or pyroclastic density currents and their fine grain size coupled with poor exposure, can hinder interpretations of their depositional origin, which is vital if using ash layers for hazard assessment. A new method of discriminating between these two types of deposit is presented in this thesis. Samples of unequivocal depositional origin were collected from formations within the Bandas del Sur Group and their fabrics, analysed using Anisotropy of Magnetic Susceptibility (AMS). This revealed differences in the distribution of susceptibility axes, the imbrication of the magnetic foliation and the strength and shape of the anisotropy between the two types of deposit. However the discrimination using the traditional AMS plots was found to be equivocal in some instance, so a new discriminant plot has been devised, which can successfully discriminate between the two types of ash layer. AMS has been used to categorise cross-stratified, stratified, diffusely bedded and massive lithofacies, and to interpret flow-boundary conditions and depositional mechanisms. Samples were collected from ignimbrites and ash layers from the Bandas del Sur Group and their AMS fabrics compared. The distribution of the magnetic susceptibility axes on the stereonets has been used to infer flow-boundary conditions; girdle distributions represent more tractional processes, whereas well-grouped distributions represent more granular processes and random distributions represent fluid escape dominated flow-boundary zones. The most significant outcome was the recognition of different types of massive deposit, based on variations in the distribution of the susceptibility axes, which are interpreted to have been deposited at a fluid-escape dominated flow-boundary influenced by other processes (traction and/or granular shear). This indicates that not all massive deposits are emplaced in the same way.

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Matthieu, Branellec. "Impact du mode de propagation des fronts orogéniques sur la géométrie, la localisation et la chronologie de la déformation : Cas du Bassin de Neuquén, (Argentine)." Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3042/document.

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Cette thèse traite de l’enregistrement de la déformation, à différentes échelles de temps et d’espace dans la chaîne plissée de Malargüe et le bloc de San Rafael, situés dans la partie septentrionale du bassin de Neuquén en Argentine. La première partie du travail comprend une analyse de la déformation finie (chaîne de Malargüe) et de la déformation active (bloc de San Rafael) à l’échelle macroscopique. De manière générale, les coupes structurales régionales proposées mettent clairement en évidence le rôle l’héritage structural lié aux structures générées lors de l’ouverture du bassin au Jurassique. Nous montrons également que les mécanismes de soulèvement actuels du bloc de San Rafael à l’est reprennent les modalités de la déformation d’âge Miocène dans la chaîne. Contrairement au mode de structuration des prismes critiques classiques caractérisés par la localisation de la déformation le long d’un niveau de décollement, la structuration de la chaîne est ici issue d’une déformation distribuée plus largement dans la lithosphère. A l’échelle de l’endommagement mesoscopique, la fracturation régionale nous a permis d’enregistrer les différents champs de contraintes régionaux liés aux phases de raccourcissement depuis le domaine pré-plissement jusqu’à la phase syn-plissement. Ces différentes phases sont en accord avec la cinématique de la convergence de la plaque Nazca depuis le Crétacé supérieur. A l’échelle microscopique, l’analyse des propriétés de susceptibilité magnétique des roches met en évidence, d’une part, une compartimentalisation de la déformation à l’échelle de la matrice liée à l’héritage structural extensif. D’autre part, la distribution spatiale de cet endommagement ne démontre pas l’existence de gradient clair des fabriques magnétiques depuis l’avant-pays vers les zones internes ce qui confirme le caractère atypique du système Andin à la latitude de 35°S. Ce dernier étant principalement contrôlé par une déformation distribuée, liée à l’héritage structural et singulièrement différente de celle attendu dans le cadre de la théorie du prisme critique
This PhD project deals with multiscale record of the tectonic signal in the Malargüe fold-and-thrust-belt (MFTB) located in the northern part of the Neuquén basin (Argentina). The first results presented rely on the study of the macroscopic finite strain in the fold-belt and the characterization of the active deformation of the San Rafael Block uplift. The cross-sections we produce show that structural inheritance related to the Jurassic extension is the main parameter controlling the belt structure. In addition we proposed that the building mechanisms that controlled the MFTB evolution by Miocene times are the same than those triggering the present day San Rafael block uplift. The second part of this work is dedicated to mesoscopic strain pattern analysis recorded by fracture networks. Throughout the MFTB, we are able to describe the occurrence of four main fractures sets emplaced in several stress regime that are linked (1) to the inheritance and (2) to the well-known compression phases from pre-folding to syn-folding settings. Finally the third part of this work describes the microscopic damage recorded by the anisotropy of magnetic susceptibility method. We mainly evidence that there is no clear gradient of magnetic fabrics from foreland to hinterland and that deformation is compartmentalized by structural inheritance. This atypical pattern of magnetic fabrics succession reveals that the matrix damage is governed by the same strain distribution as those observed at macroscopic scale thus providing a supplementary argument to consider the Andean system at these latitudes as singularly different from a classical Coulomb wedge

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Vukadinovic, Nicolas. "Excitations magnétiques hautes fréquences dans des films minces à aimantation non uniforme." Habilitation à diriger des recherches, Université Paris Sud - Paris XI, 2003. http://tel.archives-ouvertes.fr/tel-00003276.

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L'étude des excitations magnétiques de faible amplitude existant dans des films minces à aimantation non uniforme dans la gamme des hautes fréquences, typiquement entre quelques dizaines de MHz et quelques dizaines de GHz, constitue le sujet de ce mémoire. Le cas idéal de films magnétiques possédant une anisotropie perpendiculaire et présentant une configuration d'équilibre de l'aimantation sous forme de rubans parallèles et périodiques est étudié en détail. Dans le cas de films à forte anisotropie perpendiculaire, les spectres théoriques de susceptibilité dynamique calculés à l'aide de modèles analytiques puis, à partir de simulations numériques 2D de micromagnétisme dynamique, font apparaître des excitations localisées soit à l'intérieur des domaines magnétiques soit à l'intérieur des parois magnétiques. Ces résultats ont été comparés de façon satisfaisante avec des résultats expérimentaux issus de mesures de résonance ferromagnétique réalisées sur des films monocristallins de grenats ferrimagnétiques. Toutefois, les largeurs de raie expérimentales associées aux excitations de parois excèdent celles calculées en utilisant le terme dissipatif de Gilbert. Dans le cas de films à faible anisotropie perpendiculaire, les spectres théoriques de susceptibilité dynamique présentent de multiples excitations magnétiques liées à la forte hétérogénéité des configurations d'équilibre de l'aimantation de type rubans faibles. Les analyses modales effectuées à partir des simulations micromagnétiques dynamiques indiquent l'existence de modes de surface et de volume localisés dans différentes régions de spins à l'intérieur du film. L'influence de différents paramètres (anisotropie perpendiculaire, épaisseur du film, champ magnétique statique) sur les principales caractéristiques des spectres (nombre de résonances, fréquences de résonance, intensités et largeurs de raie) est ensuite étudiée. Ces simulations micromagnétiques dynamiques permettent d'interpréter des spectres expérimentaux complexes de perméabilité dynamique mesurés sur des films ferromagnétiques amorphes. Quelques perspectives concernant la dynamique de l'aimantation de faible amplitude dans différents objets magnétiques sont ensuite présentées.

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Cavalcante, Geane Carolina Gonçalves. "Evolução tectônica e reologia de uma crosta orogênica quente: o caso do Anatexito Carlos Chagas, Faixa Araçuaí (Leste do Brasil)." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-11022014-143756/.

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A Faixa Araçuaí foi formada no Neoproterozóico a partir da colisão E-W entre os continentes Sul-Americano e Africano. Sua porção leste compreende uma extensa área migmatítica (~300 km de comprimento por 50-100 km de largura) onde afloram anatexitos e leucogranitos (unidade Carlos Chagas), kinzigitos e granulitos migmatizados, que provavelmente são o registro de uma ampla fusão parcial da crosta intermediária a inferior. Observações de campo associadas com evidências micro-estruturais indicam que a deformação ocorreu quando as rochas estavam incompletamente solidificadas. Estimativas de temperaturas sincinemáticas realizadas a partir do geotermômetro TitaniQ (titânio-em-quartzo) indicam que a temperatura mínima para a cristalização de cristais de quartzo é ~750°C. Tais temperaturas combinadas com composição química de leucossomas dos anatexitos sugerem que a viscosidade das rochas crustais foi reduzida para pelo menos 108 Pa s. Baixo valor de viscosidade associado às evidências de campo e de micro-estruturas são consistentes com a geração de no mínimo 30% de volume de magma durante a orogênese. Grandes quantidades de magma promovem um drástico enfraquecimento da resistência mecânica das rochas à deformação, e atestam que a crosta anatética do extremo leste da Faixa Araçuaí representa um análogo de litosferas quentes (hot orogen), tal como a Himalaiana. Investigação mineralógica detalhada permitiu caracterizar um comportamento dominantemente paramagnético para os anatexitos e ferromagnético para os granulitos. Medidas de orientação preferencial cristalográfica (OPC) a partir da técnica de EBSD (electron backscatter diffraction) revelam que a foliação magnética surge, sobretudo, a partir da orientação preferencial dos eixos [001] da biotita orientados perpendicularmente ao plano de fluxo. Contudo, dada a fraca anisotropia linear desse mineral, apenas uma secundária contribuição de sua subtrama foi observada para a origem da lineação magnética (k1). A correspondência entre os eixos [001] de feldspatos e k1 ocorre devido a OPC de pequenas inclusões de ilmenita que imitam a OPC de seus minerais hospedeiros. Correlação entre k1 da Anisotropia de Remanência Anistéretica (ARA) e k1 da Anisotropia de Suscetibilidade Magnética (ASM) demonstra que, na escala do espécime, a lineação magnética tem uma contribuição da anisotropia dos minerais ferromagnéticos. Assim sendo, a lineação magnética nos anatexitos é o resultado da combinação da trama cristalográfica de feldspatos e de biotita com o alinhamento preferencial de grãos ferromagnéticos. Medidas de ASM realizadas para recuperar a trama mineral e investigar o fluxo nos migmatitos revela um padrão de deformação complexo, no qual, em função das direções de lineação, especialmente, é possível caracterizar três setores estruturais. A porção norte (região estrutural 1) com foliações dominantemente sub-horizontais e lineação fortemente orientada na direção NW-SE representa uma região de escape tectônico que ocorre através de um fluxo horizontal de canal (channel flow). Fluxos de canais possivelmente resultam da atuação de forças gravitacionais (gravity-driven flow). O setor sul (regiões estruturais 2 e 3) com variadas direções de foliação (NE-SW, E-W e NW-SE) e lineações com caimentos para Norte e Oeste, provavelmente refletem um regime de fluxo influenciado, sobretudo, pela tectônica de convergência E-W (collision-driven flow). Ambos os setores sugerem que na escala regional o fluxo crustal registrado pelos migmatitos resulta de um regime de deformação que envolve forças gravitacionais, devido a carga topográfica da crosta superior sobreposta à crosta intermediária parcialmente fundida, com viscosidade baixa, e forças tectônicas, associadas à colisão entre os continentes Sul-Americano e Africano.
The Araçuaí belt was formed by the collision between South American and African protocontinents during the Neoproterozoic. Its eastern part consists of an extensive migmatitic area (~300 km long x 50-100 km wide) where crop out anatexites and leucogranites (Carlos Chagas unit), migmatitic kinzigites and granulites that probably are the record of a widespread partial melting of the middle to lower crust. Field observations associated with microstructural evidences indicate that the deformation occurred when the rocks were incompletely solidified. Synkinematic temperature estimates realized using the TitaniQ (titaniun-in-quartz) geotermomether suggest that the minimum temperature for the quartz crystallization is ~750°C. Such temperatures combined with bulk rock composition of leucosome in the anatexites suggest that the viscosity of crustal rocks was dropped to at least 108 Pa s. Low viscosity values associated with field and microstructural evidences are consistent with the generation of at least 30% volume of melt during the orogeny. The presence of large volumes of melt promotes a drastic weakening of the mechanical strength of rocks and suggests that the anatectic crust of the eastern Araçuaí belt represents an analogue of present day hot orogen such the Himalayas. Detailed mineralogy investigation permitted to characterize the paramagnetic behaviour of the anatexites and the ferromagnetic behaviour of the granulites. Crystallographic preferred orientation (CPO) measurements using the EBSD (Electron Backscatter Diffraction) technique reveal that the magnetic foliation results from the preferred orientation of the biotite [001] oriented normal to the flow plane. However, given the feeble linear anisotropy of this mineral, only a subsidiary contribution of its subfabric to the origin of the magnetic lineation (k1) was observed. Correspondence between [001] of feldspars and k1 is due to the CPO of small inclusions of ilmenite that mimic the CPO of their host minerals. Correlation between k1 of the Anisotropy of Anhysteretic Remanent Magnetization (AARM) and k1 of the Anisotropy of Magnetic Susceptibility (AMS) demonstrate that, at the specimen scale, the magnetic lineation has a contribution of the anisotropy of the ferromagnetic minerals. AMS measurements realized to recover the mineral fabric and investigate the migmatitic flow field revealed a complex strain pattern in which, considering the lineation trends, especially, it is possible to characterize three structural sectors. The north region (structural sector 1) with foliations dominantly sub-horizontal and lineation trending NW-SE is interpreted as a region of tectonic escape that may represent a horizontal channel flow. This oblique tectonic escape probably results from gravity forces (gravity-driven flow). The Southern region (structural sectors 2 and 3) with variable trending foliations (NE-SW, E-W and NW-SE) and lineation plunging to North and West, probably reflect a flow regime dominantly influenced by the E-W convergence of the African and South-American continents (collision-driven flow). Altogether, the characteristics of the various domains suggest that the deformation of the partially molten middle crust of the Araçuaí belt was the result of the combination of gravity forces due to the topographic load and tectonic forces due to the convergence between the African and South-American continents.

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Азарх, Даниїл Павлович. "Неоднорідні магнітні конфігурації та їх вплив на динамічні властивості феромагнітних плівок з просторово модульованими параметрами." Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/26159.

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Магістерська дисертація складається зі вступу, 2 розділів, висновків, та переліку літератури з 122 найменувань, викладених на 79 сторінках друкованого тексту. В околі фазових переходів термодинамічні потенціали різних фаз вирівнюються. Це дає можливість малими змінами зовнішніх параметрів таких як електричне, магнітне поля або механічний вплив, керувати міжфазним розподілом. Оскільки властивості магнітних матеріалів сильно залежать від фазового розшарування, це дає можливість створювати керовані функціональні елементи пристроїв спінтроніки, магноніки, сенсоріки тощо. Показано, що в феромагнітних плівках з неоднорідною анізотропєї може бути сформована міжфазна границя при певних значеннях і напрямках магнітного поля. Ця границя має стійку магнітну конфігурацію. Вона орієнтована паралельно до площини плівки і відокремлює області з різним характером намагніченості. У змінному магнітному полі коливання міжфазних границь може супроводжуватися резонансом. Визначено поля та частотні залежності компонент тензора магнітної сприйнятливості. Показано, що коефіцієнти сприйнятливості при резонансі надзвичайно чутливі до напрямку зовнішнього магнітного поля. На основі рівнянь динаміки намагніченості Ландау – Ліфшиця описані особливості формування міжфазної границі в умовах просторової модуляції константи анізотропії по товщині плівки. Отримані рівняння Лагранжа для колективних змінних поля намагніченості, на підставі яких досліджена динаміка коливань міжфазної границі у змінному магнітному полі. Магнітна система, розглянута в роботі, може бути використана в якості високочутливого гостроспрямованого детектора магнітного поля. Результати роботи були представлені на двух конференціях: 1. Yu.I. Dzhezherya, D.P. Azarkh, V.V. Kruglyak Magnetic resonance in a ferromagnetic film with modulated anisotropy under the orientational phase -transition // 4th International research and practice conference NANOTECHNOLOGY and NANOMATERIALS NANO - 2016 August 24 - 27, 2016, Lviv, Ukraine 2. Yu.I. Dzhezherya, A.O. Khrebtov, V.V. Kruglyak, D.P. Azarkh Sharp-pointed susceptibility of ferromagnetic films with inhomogeneous in thickness magnetic anisotropy // 5th International research and practice conference NANOTECHNOLOGY and NANOMATERIALS NANO - 2017, August 2 3 - 26, 2017.Chernivtsi, Ukraine А також вийшли дві статті: 3. Y.I. Dzhezherya, D.P. Azarkh, E.S. Klimuk, A.O. Khrebtov Magnetic resonance of the interphase boundary in ferromagnetic films with modulated anisotropy under orientational phase transition conditio ns// Low Temperature Physics 44 (1), 45 - 49 4. Y.I. Dzhezherya, A.O. Khrebtov, D.P. Azarkh, S.P.. Kruchinin Sharp - pointed susceptibility of ferromagnetic films with magnetic anisotropy inhomogeneous in thickness // International Journal of Modern Physics B, 1840034

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Lyra, Diego da Silveira. "Anisotropia de Susceptibilidade Magnética (ASM) aplicada ao modelo de posicionamento do Granito Butiá: um granito sintectônico peraluminoso do sul do Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/173883.

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O período pós-colisional do Ciclo Brasiliano/Pan-africano é marcado no sul do Brasil pela ocorrência de granitos metaluminosos e peraluminosos, controlados por um sistema transcorrente de zonas de cisalhamento (ZC). No Rio Grande do Sul (RS), a Zona de Cisalhamento Transcorrente Dorsal de Canguçu (ZCTDC), de cinemática sinistral e direção NE, é a principal estrutura que condicionou o posicionamento desses granitos (ca. 634 – 610 Ma). Entretanto, o Granito Butiá (GB – 629 Ma), localizado a noroeste da ZCTDC, ocorre como um corpo alongado de direção NNW que intrude rochas de alto grau metamórfico do Complexo Várzea do Capivarita (ca. 650 Ma). O GB possui trama planar bem desenvolvida (S>L), cuja foliação mergulha com alto ângulo para NNW; apesar de raramente apresentar lineação, seu posicionamento é interpretado como sintectônico a uma ZC transcorrente de cinemática destral. Dessa forma, um estudo de anisotropia de susceptibilidade magnética (ASM) foi realizado no GB, com o objetivo de melhor delimitar os mecanismos de seu posicionamento e relacioná-los com o sistema regional de zonas de cisalhamento. No total, 492 espécimes (180 cilindros) foram coletadas em 16 sítios, distribuídos no corpo principal do GB. A mineralogia magnética foi investigada através de curvas termomagnéticas, curvas de histereses e de aquisição de magnetização remanente isotermal, e detalhada com microscopia eletrônica de varredura em amostras representativas. Essas análises demonstram o domínio de fases paramagnéticas e uma pequena contribuição de minerais de baixa coercividade (e.g., magnetita, titanomagnetita) e alta coercividade (e.g., hematita). Apesar disso, a trama magnética é controlada exclusivamente por cristais paramagnéticos de biotita. A susceptibilidade magnética total é baixa e varia entre 0,1 e 8x10-5 SI. O parâmetro de forma (T) varia de 0,272 a 0,908 e o grau de anisotropia (P) varia de 1,073 a 1,266, aumentando do centro em direção as margens do GB. A presença de par S-C destral de origem magmática e microestruturas de deformação em alta temperatura (~650°C) confirmam que a deformação atuava durante o processo de cristalização. Esses elementos, junto à análise da trama magnética, sugerem que a ascensão e o posicionamento do magma foram controlados por uma ZC transcorrente de direção NNW e cinemática destral. Próximo as rochas encaixantes, os elipsoides magnéticos são fortemente oblatos, a foliação mergulha com alto ângulo para W ou E, e a lineação têm alto a moderado caimento, sugerindo significante achatamento e domínio de uma componente de cisalhamento puro de deformação. Longe das margens, a lineação tem baixos caimentos, paralelos a direção da foliação (NW-NNW), sugerindo um transporte horizontal e domínio de uma componente de cisalhamento simples de deformação, que promoveu o estiramento. No nordeste do corpo, a presença de roof pendants e menores ângulos de mergulho da foliação sugerem proximidade com a cúpula. A combinanção de bouyoancy forces e da partição da deformação regional, em cisalhamento puro e simples durante o posicionamento do GB, está de acordo com um regime transpressivo. Esses resultados também sugerem uma relação no tempo-espaço entre a ZC que controlou o posicionamento do GB e a ZCTDC. Possivelmente, elas formavam um par conjugado do mesmo sistema transcorrente durante o estágio pós-colisional do Ciclo Brasiliano/Pan-africano no sul do Brasil.
The post-collisional stage of the Brasiliano/Pan-African Orogenic Cycle in Southern Brazil is marked by metaluminous and peraluminous granites controlled by a transcurrent shear zone system. In the Rio Grande do Sul State, southernmost Brazil, the sinistral, NE-trending Dorsal de Canguçu Transcurrent Shear Zone (DCTSZ) is the best known structure that conditioned these peraluminous granites (ca. 634 – 610 Ma). However, the NNW-elongate Butiá Granite (BG – 629 Ma) is emplaced to the northwest of the DCTSZ, intrusive in the high-grade Várzea do Capivarita Complex (ca. 650 Ma). The BG has a S>L fabric, which foliation steeply dips towards NNW. Despite its poorly-developed linear fabric, BG emplacement is interpreted to have been controlled by a dextral transcurrent shear zone. Thus, anisotropy of magnetic susceptibility (AMS) study was performed in the BG aiming to constrain its emplacement mechanism and the relation of the granite with the regional shear zone system. A total of 492 specimens (180 drill cores) were obtained through 16 sites distributed along the BG main body. Magnetic mineralogy was investigated by hysteresis loops, thermomagnetic and IRM acquisition curves, and a complementary SEM analysis in representative samples. These experiments show a dominant contribution of paramagnetic phases and a small content of low-coercivity (e.g., magnetite and titanomagnetite) and highcoercivity (e.g., hematite) remanence-carrying minerals. In spite of the presence of minor ferromagnetic grains, the BG magnetic anisotropy fabric is interpreted as dominantly controlled by paramagnetic biotite crystals. The bulk magnetic susceptibility ranges between 0.1 and 8.0×10−5 SI. Shape parameter (T) ranges from 0.272 to 0.908, and anisotropy degree (P) ranges from 1.073 to 1.266, increasing from the inner portion of the pluton to its margins. The presence of dextral S-C magmatic fabric and high temperature (ca. 650 °C), solid-state deformation at the margins confirms that the pluton was deformed during its cooling process. Such features, together the magnetic fabric analysis, suggest that magma ascent and emplacement were controlled by a NNW-trending dextral transcurrent shear zone. Close to the host-rocks, magnetic foliation dips steeply towards W or E, and magnetic lineation plunges steeply to moderate, displaying strongly-oblate ellipsoids. This is interpreted as a result of shortening and the significantly pure-shear component of deformation operating close to the host-rocks. Shallow-plunging lineation parallel to the NWto NNW-striking foliation is found away from the pluton margins, which is related to the horizontal displacement, where the simple-shear component of deformation was more effective, resulting stretching. Foliation becomes less steep towards the BG northeastern portion and the presence of roof pendants in this area suggests the proximity to the roof zone. The combination of buoyancy forces and the partitioning of regional strain into simple and pure shear are in accordance with a transpressive regime. These results also suggest a time-space relationship between the NNW-dextral shear zone that controlled the emplacement of the Butiá Granite and the sinistral, NE-trending DCTSZ, responsible for the emplacement of peraluminous granites. Possibly, these zones formed a conjugate pair during the transcurrent deformation of the early post-collisional stage of the Brasiliano/PanAfrican Cycle in southernmost Brazil.

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Rochette, Pierre. "La susceptibilité anisotrope des roches faiblement magnétiques : origines et applications : [thèse soutenue sur un ensemble de travaux]." Phd thesis, Grenoble 1, 1988. http://tel.archives-ouvertes.fr/tel-00745513.

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La susceptibilité des roches faiblement magnétiques a une origine complexe : aux grains ferromagnétiques se rajoutent des contributions dla-, para-, et antlferromagnétiques. Celles-ci ont été mises en évidence grâce à de nouvelles techniques de mesures magnétiques en champ fort et température variable. Les propriétés liées aux phyllosilicates et carbonates ferromagnétiques, à la pyrrhotite et à la goethite ont été particulièrement étudiées. La susceptibilité magnétique ainsi analysée permet de suivre l'évolution pétrologique des roches, en particulier en fonction du métamorphisme et de l'altération. L'anisotropie de susceptibilité magnétique doit être interprétée en fonction de la nature et de l'orientation préférentielle des grains magnétiques. En prenant en compte les mécanismes de la déformation on a accès ainsi à certaines données structurales difficilement appréhendées par les méthodes classiques du fait de la sensibilité et la rapidité des mesures magnétiques ; il s'agit en particulier des linéatlons d'étirement en zones peu déformées. Les éléments d'une modélisation quantitative de la relation entre déformation et anisotropie magnétique sont discutés. Les études de cas ont porté sur des roches sédimentaires non métamorphiques à mésozonales, principalement alpines, sur différents granites et sur des péridotites.

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Kergaravat, Charlie. "Dynamique de formation et de déformation de minibassins en contexte compressif : exemple du bassin de Sivas, Turquie Approche terrain et implications structurales multiéchelles." Thesis, Pau, 2016. http://www.theses.fr/2016PAUU3005/document.

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Cette thèse porte sur les interactions entre les déformations halocinétiques locales au sein des mini-bassins salifères et les déformations régionales compressives. L’étude s’appuie sur une analyse structurale multi-échelle détaillée d’une province à mini-bassins se développant dans le bassin d’avant pays de Sivas (Turquie). Une analyse de terrain approfondie, associée à une étude de données de subsurface, permet de proposer une révision des cartes géologiques ainsi qu’une évolution tectonosédimentaire identifiant les déformations liées à la tectonique salifère et celles liées à la propagation de la ceinture de plis et de chevauchements dans l’avant-pays. A partir de l’Eocène supérieur, le fluage del’évaporite autochtone, initié et entretenu par le chargement sédimentaire différentiel ainsi que par la déformation compressive, permet la formation d’une première génération de mini-bassins. Ces minibassins, constitués par une formation continentale Oligocène, vont être recouverts par une nappe d’évaporite allochtone accueillant une seconde génération de mini-bassins constitués de formations continentales et marines Oligo-Miocène. L’initiation du domaine de mini-bassins secondaires est caractérisée par une distribution polygonale du réseau de diapirs et de murs d’évaporites. Ces mini-bassins enregistrent localement les effets de la tectonique salifère par le développement d’une grande variété de structures halocinétiques à différentes échelles telles que les séquences halocinétiques unitaires (crochet et éventail), séquences composites (tabulaire ou fuseau) et megaflaps. Une série de modélisation analogique préliminaire amontré que ces structures peuvent se développer avec ou sans l’application d’une compression aux limites. De plus, les analogies géométriques entre les mini-bassins de Sivas et les provinces salifères connues suggèrent que la dynamique de formation de ces mini-bassins est au premier ordre contrôlée par le chargement sédimentaire différentiel, découplé partiellement de la compression régionale. Néanmoins, l’analyse du réseau de fractures et de l’endommagement matriciel souligne l’enregistrement précoce de la déformation compressive régionale lors de l’initiation des mini-bassins.L’influence du raccourcissement sur la structuration de la province à mini-bassins s’exprime de manière croissante par l’écrasement des corps salifères permettant : (i) le développement de dépocentres linéaires préférentiellement perpendiculaire à la direction de raccourcissement, (ii) l’émergence de corps allochtones d’évaporites en surface, ainsi que (iii) la rotation et translation des mini-bassins. Cette province à mini-bassins génère une discontinuité dans la propagation et l’accommodation de la déformation compressive : la déformation compressive est accommodée auniveau du réseau polygonal de murs d’évaporites formant des structures multidirectionnelles. De plus, cette concentration de la déformation par écrasement des structures salifères entraine la remobilisation des évaporites vers l’avant-pays générant alors un nouveau système salifère
This doctoral work studies the interaction between withdrawal of minibasins and regional shortening during evolution of a foreland fold-and-thrust belt. This is achieved by a multiscale structural analysis of the Sivas Basin (Turkey). Extensive field work and regional seismic lines interpretations helped to build a new and detailed geologic map of the central Sivas Basin and to provide a new tectonosedimentary framework highlighting the influence of salt tectonics and the regional shortening, starting in the Late Eocene by the autochthonous evaporite deposition. This level is remobilized by the northward migrating sedimentary load, shortening and tilting of the basin southern margin during propagation of the foreland fold-and-thrust belt. Evaporite flow is recorded by the withdrawal of a primary generation of continental Oligocene minibasins which are then covered by an evaporite canopy. The canopy extending northward allows the development of second generation of continental to shallow marine mini-basins from Oligocene to Middle Miocene. Secondary minibasins initiation in the central part of the Basin, is characterized by sub-circular minibasins surrounded by polygonal diapirs and walls. Flanking these minibasins, a large variety of halokinetic structures is described: halokinetic sequences (hooks and wedges), composite halokinetic sequences and megaflaps. Preliminary sand-box modeling study suggests the development of thesehalokinetic structures both with and without shortening. Furthermore, minibasins geometries are closely similar to those imaged or mapped in other salt provinces suggesting that mini-basin withdrew is first control by sedimentary load, probably due to decoupling by the salt. However, the fractures and anisotropy of magnetic susceptibility analyses suggests the record of shortening since the minibasins initiation. The increase influence of regional shortening on the minibasins domain is expressed by salt walls and diapirs squeezing inducing: (i) the development of linear mini-basins perpendicular to the shortening direction, (ii) salt sheet emplacement and (iii) the translation/rotation of minibasins. The minibasins province produces a discontinuity for the fold-and-thrust belt propagation. Indeed, the minibasins province accommodates the shortening deformation along the polygonal network of salt walls and diapirs forming multidirectional structures. Furthermore, the regional shortening accommodation by salt structures squeezing produce an evaporitic remobilization and migration of a salt canopy toward the foreland basin
Bu doktora tezi/çalışması, bir önülke kıvrım ve bindirme kuşağının evrimi sırasında minihavzaların çekilmesi ve bölgesel kısalma arasındaki etkileşimi konu edinir. Çoklu ölçekteki bu yapısal analiz Sivas Havzası (Türkiye) ölçeğinde gerçekleştirilmiştir. Kapsamlı saha çalışması ve bölgesel olarak sismik kesitlerden ortaya çıkarılan yorumlamalar, Sivas Havzası’nın orta kesiminde detaylı bir jeolojik haritalama yapımına yardımcı olmuş ve otokton evaporit depolanmasının başladığı Geç Eosen’den başlayarak havza için tuz tektoniği ve bölgesel kısalmanın etkisindeki yeni bir tektono-sedimanter çatının ortaya çıkarılmasına neden olmuştur. Söz konusu seviye, önülke kıvrım ve bindirme kuşağının ilerlemesisüresince kuzeye doğru sedimanter dolgunun göçüyle birlikte havzanın güney kenarında kısalıma uğrayarak ve eğim kazanarak remobilize olmuştur. Evaporit akışı, kıtasal Oligosen minihavzalarının ilksel olarak oluşumundan sonra çekilmesine bağlı olarak gözlenmiş ve sonrasında evaporit yaygılarıyla örtülmüştür. Kuzeye kadar uzanan bu yaygı, Oligosen-Orta Miyosen arasında kıtasaldan sonra sığ denizel tipteki ikincil minihavzaların gelişimine de neden olmuştur.Havzanın orta kesimindeki ikincil minihavza başlangıcı, poligonal diyapir ve duvarlar tarafından çevrelenen dairesel minihavzalarla karakterize olur. Bu minihavzaların kanatlarında halokinetik yapılar tanımlanmıştır. Kanca (hook) ve kama (wedge) tiplerde olmak üzere halokinetik seriler, kompozit halokinetik seriler ve megaflaplar bu yapılar arasında sayılabilir. Çalışmanın başlangıcında yapılan kum kutusu model deneyi, bu halokinetik yapıların kısalmayla veya kısalma olmaksızın geliştiğini göstermiştir. Buna ek olarak minihavzaların geometrisi, muhtemelen tuzun ayrışmasından dolayı tortul yükün ilkkontrolünden dolayı çekilen diğer tuz bölgelerinde önerilen haritalanmış minihavzalara benzerdir. Bununla birlikte kırık ve manyetik suseptibilite analizleri, minihavzaların başlangıcından itibaren kısalmanın kayıt edilebilmesi hakkında fikir vermektedir. Minihavza bölgelerindeki bölgesel kısalımın artışı, tuz duvarları ve diyapirlerin sıkışmasıyla birlikte(i) kısalma yönüne dik durumdaki çizgisel minihavzaların gelişimi, (ii) tuz örtülerinin yerleşimi ve (iii) minihavzaların yer değiştirmesi veya dönmesiyle açıklanır. Minihavzalar bölgesi, kıvrım ve bindirme kuşağının gelişimi için bir süreksizlik üretir. Aslında, minihavzalar birçok yönde yapılar oluşturarak tuz duvarları ve diyapirlerin polygonal şekildeki yerleşimi boyunca kısalma deformasyonuna eşlik eder. Üstelik, tuz yapılarının eşlik ettiği bölgesel kısalma önülke havzalarına doğru evaporitik bir göçe de neden olmaktadır

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Falvard, Simon. "Application de la microtomographie par rayons X à l'étude des dépôts de tsunamis." Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22686/document.

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L’étude des dépôts de tsunamis est une science relativement jeune, et si de nombreux progrès ont été faits, en particulier au cours des trois dernières décennies, les techniques disponibles à l’heure actuelle ne permettent pas l’étude exhaustive des dépôts, que ce soit à cause de problèmes de conservation, fréquemment rencontrés, ou de limites liées aux techniques analytiques elles-mêmes. En effet, leur résolution spatiale s’avère insuffisante pour les dépôts fins (fractions sableuses et inférieures), soit par leur principe même (absence de visualisation en trois dimensions sur des lames minces, par exemple), soit à cause des techniques d’échantillonnage dont elles dépendent. Ce travail a permis d’explorer les applications d’une technique analytique jusqu’à présent inutilisée dans ce domaine, la microtomographie par rayons X, appliquée à trois dépôts de tsunamis : les dépôts du tsunami de Lisbonne en 1755 sur les côtes Andalouses, ceux d’un tsunami causé en 1996 dans le Lac Karymskoye au Kamchatka, et un potentiel dépôt de tsunami datant de l’Holocène à Ninety Mile Beach, sur le littoral ouest de l’Australie. Les problématiques liées aux techniques d’échantillonnage et au traitement des données brutes et à leur exploitation sont passées en revue et les solutions retenues sont exposées. Les résultats obtenus sont comparés à ceux obtenus par l’utilisation de techniques analytiques dont la pertinence et l’utilité ont été démontrées lors de précédentes études. Cette technique se révèle extrêmement utile pour les analyses structurales (organisation interne des dépôts), texturales (distributions de tailles de grains, fabrique sédimentaire et dynamiques d’écoulements), ainsi que les analyses de composition (abondances en bioclastes et en minéraux lourds par exemple). Le croisement des études structurales et texturales du dépôt du tsunami de 1755 mettent en avant des dynamiques de mise en place allant parfois à l’encontre des scenarii généralement admis et offre un nouveau point de vue sur les dépôts de tsunami
The study of tsunami deposits is a relatively young science, and even if substantial progress has been made (especially during the last three decades) the techniques available at present day do not allow exhaustive studies of the deposits, weither poor conservation of the deposits, which is a common problem, is to blame, or because of limitations of the techniques themselves. Their spatial resolution often appears to be insufficient for fine deposits (sand size fractions and finer) because of their working principle (lack of three dimensional visualisation of structures on thin sections for instance) or because of the sampling techniques they depend on. This work allowed exploring the applications of an analytic technique, X-ray computed microtomography, which had to this day never used before for the study of tsunami deposits. Three distinct case studies have been made: deposits from the 1755 Lisbon tsunami on the western coast of Spain (Andalusia), deposits from the 1996 tsunami triggered in Karymskoye Lake, and a potential mid-Holocene tsunami deposit at Ninety Mile Beach, western Australia. Problematic linked to sampling techniques and raw data processing and exploitation are addressed. Chosen solutions are exposed. The results are compared to those obtained using techniques whose relevance and usefulness have been proven in previous studies. This technique proves to be extremely useful for structural (deposits inner organisation), textural (grain size distribution, sedimentary fabrics and flow dynamics), and composition (bioclasts and heavy minerals abundances) analyses. Crossing structural and textural analysis of the 1755 Lisbon tsunami deposit unravels deposition modes which go against the usually admitted scenario and offers a new point of view on tsunami deposits

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Perinotto, Hélène. "Dynamique de mise en place des avalanches de débris sur les flancs aériens des volcans insulaires : le cas de La Réunion." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0414/document.

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Les avalanches de débris, qui résultent du démantèlement des flancs des édifices volcaniques et montagneux, sont des écoulements granulaires rapides et dangereux dont le monteur est la gravité et qui présentent des distances de transport extrêmement importantes. La dynamique de leur mise en place et leurs mécanismes de transport permettant cette très grande mobilité sont des phénomènes qui demeurent encore mal compris. De nombreux modèles existent pour expliquer la grande mobilité des avalanches de débris et incluent des processus basés sur la lubrification ou la fluidification de la masse granulaire mais également sur le phénomène de désintégration dynamique des éléments. Cependant la grande majorité des modèles proposés souffre du manque d’observations de terrain et de quantification de l’évolution des matériaux au cours de leur transport au sein de la masse granulaire. Afin d’identifier les principaux mécanismes de transport des avalanches de débris, nous proposons dans ce travail une étude de terrain détaillée de dépôts d’avalanches de débris volcaniques qui résultent du démantèlement d’un volcan bouclier océanique, le Piton des Neiges (île de La Réunion, océan Indien). L’approche est couplée à un examen morphométrique (dimension fractale et circularité), exoscopique et granulométrique des particules présentes dans les dépôts. Elle est complétée par l’examen de la fabrique des dépôts basée sur l’anisotropie de la susceptibilité magnétique (ASM). Les données obtenues nous permettent de mettre en évidence une évolution de la dynamique de transport et de mise en place des dépôts d’avalanches de débris depuis les zones sources jusqu’aux domaines de dépôt distaux. On montre également que la désintégration dynamique et le gonflement dispersif qui l’accompagne opèrent tout au long du transport et à toutes les échelles au-dessus d’une limite inférieure de broyage à 500 μm. En dessous de cette limite, la réduction granulométrique résulte uniquement de processus d’attrition par friction entre les particules. La grande mobilité des avalanches de débris pourrait ainsi être expliquée par l’effet combiné de la libération d’énergie élastique par la désintégration dynamique des particules > 500μm et par une réduction de la friction interne à la matrice liée aux interactions dispersives des particules fines (< 500 μm). L’ensemble des données permettent également de préciser les directions de transport et l’ampleur des avalanches de débris liées aux déstabilisations du massif du Piton des Neiges
Debris avalanches, resulting from flank collapses that shape volcanic and mountainous edifices are rapidand dangerous gravity-driven granular flows that travel long run out distances. The dynamic and the transport mechanisms behind this high mobility remain poorly understood. The numerous models proposed to explain this high mobility include processes based on lubrication or fluidisation of the granular mass of the flow body, but also the dynamic disintegration of the transported particles. To date,all these proposed mechanisms lack observational support and quantification of the state of the particles of the granular mass during the transport. To identify the main transport mechanisms, we propose here detailed field studies of volcanic debris avalanches deposits resulting of flank-collapse events on an oceanic shield volcano, the Piton des Neiges (La Réunion Island, Indian Ocean). This study has been combined with morphometric (fractal dimension and circularity), exoscopic and grain-size analyses. Moreover, the fabric of the deposits has been investigated by with the characteristics of the anisotropy of the magnetic susceptibility (ASM). From these data we highlight a proximal to distal evolution of the debris avalanches transport and emplacement dynamics. We demonstrate that syn-transport dynamic disintegration continuously operates with the distance from the source down to a grinding limit of 500μm. Below this limit, the particle size reduction exclusively results from the attrition of the particles by frictional interactions. Thus, the exceptional mobility of debris avalanches may be explained by thecombined effect of elastic energy release during the dynamic disintegration of the larger clasts (> 500μm) and frictional reduction within the matrix due to the dispersive interactions between the finer particles (< 500 μm). All these data also allow to specify the transport direction and the approximate size of the debris avalanches related to the Piton des Neiges destabilisations

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Hunter, Shannon K. "Geologic and Paleomagnetic Study of the Miocene Haycock Mountain Tuff: Markagunt Plateau, Southwest Utah." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1543652864307195.

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Salazar, Carlos Alejandro. "Anisotropia de suscetibilidade magnética dos plútons Ribeirão Branco, Sguário e Capão Bonito e implicações tectônicas para a Faixa Ribeira (Domínio Apiaí, SP)." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-30062010-110127/.

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A trama de magmas graníticos alojados na crosta intermediária e superior pode-se originar pela ação de forças de corpo (ascensionais, convectivas) e/ou tectônicas. Diferentes mecanismos podem concorrer para a formação de tramas, embora a interação entre a deformação magmática e a tectônica regional seja um dos mecanismos fundamentais, notadamente nos granitos alojados em faixas orogênicas. No Domínio Apiaí da Faixa Ribeira (SP - PR), os batólitos graníticos alongados têm sido historicamente classificados como sintectônicos, ou seja, colocados durante o desenvolvimento de um arco magmático continental neoproterozóico. Os plútons menores, de forma circular a ovalada, geralmente discordantes e com típica coloração avermelhada, são considerados pós-tectônicos ou alojados após a colisão continental entre os diferentes blocos litosféricos que formaram a Faixa Ribeira. Essa classificação esquemática tem sido baseada em geoquímica e geocronologia dos granitos. Este trabalho identificou e mapeou a trama interna dos plútons sin-tectônicos (Ribeirão Branco) e pós-tectônicos (Capão Bonito e Sguário) utilizando a anisotropia de suscetibilidade magnética (ASM), de forma a inserí-los propriamente nos modelos de classificação tectônica, cujas premissas básicas são de natureza estrutural. Os granitos porfiríticos (Ribeirão Branco e Itaóca) possuem uma elevada suscetibilidade magnética (k 10-2 SI), a qual é menor (k 5 x 10-3 SI) nos granitos vermelhos (Capão Bonito e Sguário). A suscetibilidade dos granitos porfiríticos é proveniente de óxidos ferromagnéticos, notadamente magnetita pobre em Ti, que encontra-se frequentemente associada com titanita, biotita e anfibólio. Nos granitos vermelhos a suscetibilidade é gerada por magnetita, variavelmente oxidada (maghemita) e Ti-hematita (hemo-ilmenita), havendo também significativa contribuição da fração paramagnética (biotita cloritizada) à suscetibilidade total nas rochas, quando k < 10-3 SI. O grau de anisotropia magnética (P) tanto nos granitos porfiríticos como nos vermelhos é variável, porém tipicamente maior nos porfiríticos (P = 1,14, dp. 0,08), se comparado aos vermelhos (P = 1,07, dp. 0,05). A maior anisotropia de suscetibilidade no plúton Ribeirão Branco é atribuída a uma incipiente foliação detectada em vários setores do granito, que contrasta com a microestrutura aparentemente isótropa dos granitos vermelhos. O estudo da trama de silicatos no granito porfirítico Itaóca e no granito Capão Bonito mostrou que os eixos principais de anisotropia de suscetibilidade magnética e da orientação preferencial de forma (OPF) de feldspato e de biotita, são correspondentes, porém, comumente oblíquos. Essa obliquidade entre eixos é atribuída às características físicas próprias (forma, tamanho e anisotropia) dos minerais marcadores da trama. O estudo combinado da ASM e da OPF revelou ainda que P tende a crescer com a intensidade da orientação preferencial de silicatos, o que permitiu identificar os domínios de maior deformação magmática e correlacioná-los com a estrutura regional. A trama magnética do granito Ribeirão Branco organiza-se em coerência com uma tectônica regional transcorrente sinistral. Na margem ocidental deste granito, contudo, a orientação da trama é diferente do restante do maciço, tendo sido aparentemente afetada pela intrusão do granito Sguário. A trama magnética do Ribeirão Branco contrasta com a do plúton Itaóca, este último exibindo um padrão concêntrico que antecedeu ao desenvolvimento da deformação transcorrente regional. Zircões do Itaóca forneceram uma idade U-Pb (SHRIMP) concordante de 623 ± 10 Ma, atribuída à cristalização deste plúton. Dados da literatura indicam que o granito Capão Bonito é aproximadamente 15 Ma mais jovem que os batólitos de granito porfirítico. O Capão Bonito, entretanto, apresenta uma trama muito bem organizada, típica de intrusões sin-tectônicas, destacando-se excelente alinhamento da lineação magnética. No granito Sguário, o arranjo da trama é tipicamente helicoidal e, junto com a estrutura do Capão Bonito, podem ter sido organizadas em resposta a uma deformação transcorrente E-W destral. Este evento tardio estaria associado à reativação da zona de cisalhamento Ribeira, que afetou a borda sul do granito Itaóca e que contém uma componente extensional. A deformação transtensiva E-W, que favoreceu a injeção dos granitos vermelhos no Domínio Apiaí, sucederia a um evento tectonomagmático principal, que teria sido responsável pela colocação e deformação dos batólitos de granito porfirítico. A intrusão dos grandes corpos graníticos ocorreu em torno de 615 Ma e foi relacionada à convergência crustal e estiramento subparalelo à Faixa Ribeira, com a deformação localizada notadamente nas estruturas transcorrentes de direção NE-SW.
The fabric of granitic magmas emplaced in the middle and upper crustal levels can be caused by the stress action during the ascension and convection of plutons and/or tectonic strain. Several mechanisms can contribute for the previous thing, nevertheless the interaction between the distortions and tectonic is the domineering one, principally in granites located in orogenic belts. In the Apiaí domain of the Ribeira belt (SP-PR) the elongated granitic batholiths have been historically classified like syn-tectonic and them was emplaced during the development of a neoproterozoic continental magmatic arch. Small Plutons with subcircular to oval forms generally discordant with regard to the disposition of the regional structures and that in turn possess feldspars of reddish typical colour, had been considered pos-tectonic, and therefore, emplaced after the collision that joined the different litho-tectonic units that constitute the Ribeira orogenic belt. This schematic classification of these granites relicts on geochemistry and geochronology data. In this study was identified and recorded in map the internal fabric of the syn-tectonic Ribeirão Branco granite and of the pos-tectonic Capão Bonito and Sguário granites using the anisotropy of magnetic susceptibility (AMS) with the aim of inserting them appropriately in the models of tectonic classification whose basic premises are of structural nature. The porphyritic Ribeirão Branco and Itaóca granites have a high magnetic susceptibility (k = 10-2 SI), which is minor than (k = 5 x 10-3 SI) in the red granites (Capão Bonito, Sguário). In the first ones the poor Ti magnetite is the main source of susceptibility, commonly associated to titanite, biotite and amphibole. In the red granites, the susceptibility is provided by magnetite variability rusty (maghemite) and Ti - hematite (hemo-ilmenite), in addition to the significant contribution of biotite altered by hydrothermal processes. The grade of anisotropy rise (P) in the porphyritic granites (P = 1,14 SD. 0,08) and this is bigger than in the red ones (P = 1,07, SD. 0,05). In the Ribeirão Branco pluton, the high value of P is attributed to an incipient foliation detected in several sectors, which contrasts with the microstructure seemingly isotropic of the red granites. The study of the fabrics of silicates in the porphyritic granites Ribeirão Branco and Itaóca revealed that the orientations of the main axes of AMS and of shape preferred orientation (SPO) of feldspar and mafic silicates (biotite + amphibole) are congruent, nevertheless some obliquities occur. Those obliquities are attributed to the influence of the proper characteristics (form, size, anisotropy) of the marker minerals of the respective sub fabrics. In the same way, the above-mentioned study of silicates fabric demonstrated that P tends to grow up with the intensity of the SPO of silicates, which allowed to identify domains with major magmatic distortion into de granitic bodies and to correlate them with the regional structure. In general, the magnetic fabric of the Ribeirão Branco granite is organized coherently with the tectonic regional sinestral strike-slip shear zones; nevertheless, in the western sector the orientation of the magnetic fabric was likely modified by the accommodation of the Sguário granite. In the Itaóca granite, the organization of the magnetic fabric is different if compared with fabrics of the previous pluton. In Itaóca granite was recorded a fabric with a concentric organization in 623 ± 10Ma. (MSWD 0,31), according to the concordant U-Pb (SHRIMP) age in zircons obtained for the crystallization of the granite, that seems to be occurred before the strain related with the activation of the regional strike-slip shear zones. Geochronology data of the literature indicates that the Capão Bonito granite is approximately 15 Ma. younger than the batholiths of porphyritic granite. The Capão Bonito granite has an organized fabric typical of syn-tectonic intrusions that has an excellent alignment of the magnetic lineation. In the granite Sguário, the fabric has a spiral organization, in the same way as recorded in Capão Bonito, like response to a strain associated with to a small strike-slip shear zone with W-E direction. This event would be related to the reactivation of the Ribeira strike-slip shear zone, which affected the south sector of the Itaóca granite, with the participation of an extensional component. The W-E transtensive deformation that favoured the injection of the red granites in the Apiaí Domain likely was subsequent to a main tetonomagmatic event and this should have been the responsible by the emplacement and strain in the porphyritic granites. The intrusion of the big granitic bodies ~ 615 Ma. and could be it related to the convergence between crustal blocks and to the consequent stretching sub parallel of the Ribeira belt, in which the distortion was located remarkably in the strike-slip shear zones with NE-SW direction.

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26

Ball, Andrew. "Commensurabilité magnétique à longue période et anisotropie dans la série hexagonale RGa2 (R=Pr, Nd, Gd)." Grenoble 1, 1993. http://www.theses.fr/1993GRE10075.

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Les composes hexagonaux simples rga(r=gd, pr et nd) sont d'excellents candidats pour l'etude de structures magnetiques frustrees complexes resultant des interactions d'echange a longue portee. Par l'utilisation de techniques experimentales variees, nous avons mis en evidence sur ces composes des proprietes magnetiques originales et hautement complexes. Dans le cas de gdga#2, un champ magnetique induit des changements subtils dans la configuration antiphase incommensurable de la phase en champ nul. Ces processus peuvent se resumer en trois diagrammes de phases champ-temperature d'une complexite etonnante vue l'absence d'anisotropie magnetocristalline. Un modele de champ moyen periodique montre que les structures sous champ sont de type x-y en eventail, mettant ainsi en evidence l'existence d'une faible anisotropie d'echange. Les composes prga#2 et ndga#2 presentent des structures magnetiques en champ nul de type ising, confinees dans le plan hexagonal. Pres de t#n, ces structures sont incommensurables et evoluent a basse temperature vers des structures commensurables a longue periode. Dans prga#2, le champ applique induit des transitions metamagnetiques de type spin-slip et spin-flip entre differentes configurations magnetiques commensurables a longue periode. Apres une etude approfondie du champ cristallin, le modele du champ moyen periodique nous a permis d'analyser quantitativement les proprietes magnetiques principales de ce compose: chaleur specifique, aimantation, susceptibilite. . .

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27

Ramdani, Hamdane. "Contribution à l'étude d'aimants samarium-cobalt : relation entre les propriétés magnétiques et la microstructure." Rouen, 1987. http://www.theses.fr/1987ROUES034.

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Etude d'aimants frittés Sm (Co, Fe, Cu, Zr)(7,29) ayant subi des traitements thermiques différents. Mesure de la coercivité et observation de la microstructure par microscopie électronique en transmission. Corrélation entre les microstructures avant et après recuit a 830°C et les propriétés magnétiques, à partir d'un modèle basé sur la répartition des éléments d'addition

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28

Ouahioune, Nedjma. "MOKE set-upto measure magnetic anisotropy : MOKE set-upto measure magnetic anisotropy." Thesis, Uppsala universitet, Materialfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414388.

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29

Caltabeloti, Fabrizio Prior. "Alojamento e deformação de plútons graníticos da extremidade nordeste da Suíte Intrusiva Cunhaporanga (Domínio Apiaí - Faixa Ribeira, PR)." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-16082011-170032/.

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Plútons graníticos (Patrimônio Santo Antônio, São Domingos, Ouro Verde e Santa Rita) alojados na porção nordeste da Suíte Intrusiva Cunhaporanga (c. 620-590 Ma) intrudiram metassedimentos pelíticos e carbonáticos de baixo grau metamórfico do Grupo Itaiacoca. Os plútons são isótropos, de coloração cinza a rósea e composição monzo- a sienogranítica, predominando granitóides porfiríticos grossos e, secundariamente, tipos inequigranulares a equigranulares. A cartografia regional mostrou que a foliação das rochas metassedimentares encaixantes mergulha dominantemente para NE e contém uma lineação (interseção, mineral) de direção NNW-SSE. A trama metamórfica das encaixantes assume progressivamente a direção NE-SW conforme se aproxima da zona de cisalhamento transcorrente de Itapirapuã, onde quartzo-milonitos verticalizados exibem uma cinemática sinistral. A trama dos plútons foi estudada pela técnica da anisotropia de suscetibilidade magnética (ASM). Foram amostradas 40 estações (300 espécimes) no granito porfírítico Patrimônio Santo Antônio, 7 estações (48 espécimes) no granito equigranular fino de São Domingos, 9 estações (67 espécimes) no granito inequigranular de Ouro Verde e 14 estações (92 espécimes) no granito porfiritico foliado de Santa Rita. A suscetibilidade magnética média (k) do granito Patrimônio Santo Antônio é da ordem de 23,29 x \'10 POT.-3\' SI, enquanto nos granitos Santa Rita (k = 11,85 mSI), São Domingos (k = 7,43 mSI) e Ouro Verde (k = 7,46 mSI) são menores. Por outro lado, a anisotropia magnética (P = \'k IND.max\'/\'k IND.min\', onde \'k IND.max\' > \'k IND.int\' > \'k IND.min\') é menor em Patrimônio Santo Antônio (P = 1,09 ± 0,04) do que no São Domingos (P = 1,21 ± 0,09), Ouro Verde (P = 1,19 ± 0,07) e Santa Rita (P = 1,23 ± 0,11). Estudos termomagnéticos e de magnetização remanente isotermal mostraram que as propriedades magnéticas dos granitoides são dominadas pela magnetita (pobre em Ti) e, secundariamente, Ti-hematita. Sulfetos de Fe (pirita, calcopirita) ocorrem como acessórios. Os óxidos de Fe estão frequentemente associados à titanita, biotita e anfibólio e suas microestruturas são tipicamente magmáticas, exceto no granito Santa Rita onde a microestrutura apresenta evidência de recristalização pós-magmática. A foliação magnética dos maciços graníticos mergulha suave a moderadamente e, no plúton Patrimônio Santo Antônio, exibe um padrão tipicamente dômico. A lineação magnética subhorizontal orienta-se na direção NNW-SSE paralelamente ao eixo do dobramento regional das rochas metassedimentares encaixantes. Esta característica indica que os granitos são sin-tectônicos a um evento deformacional cujo controle está aparentemente relacionado ao funcionamento das grandes transcorrências regionais de direção NE-SW. A ocorrência de domos graníticos (Patrimônio Santo Antônio) e elipsóides magnéticos dominantemente prolatos (São Domingos) sugerem que a trama NNW teria sido formada por uma tectônica que combina transcorrência e extensão. Uma idade concordante U-Pb (SHRIMP) em zircão de 589 ± 6 Ma, atribuída à cristalização do plúton Patrimônio Santo Antônio, indica que a deformação que afetou o granito no estado magmático bem como suas encaixantes ocorreu nos estágios finais da formação da Suíte Intrusiva Cunhaporanga.
Granite plutons located on the northeast of Cunhaporanga Intrusive Suite (Patrimônio Santo Antônio, Ouro Verde, São Domingos and Santa Rita) are emplaced into low grade metasedimentary rocks (Itaiacoca Group) of the Apiaí Domain (Ribeira Belt). Most of these plutons are isotropic with pinkish to grey colors and their compositions vary from monzogranite to sienogranite. They are usually porphyritic and locally inequigranular and equigranular. Regional mapping revealed that the foliation of the metasedimentary host rocks dips mainly to NE while the lineation (intersection, mineral) strikes in the NNW-SSE direction. The host rocks metamorphic fabric rotates progressively to become parallel to the NE-trending Itapirapuã transcurrent shear zone. Kinematic markers such as elongated quartz grains and mica-fish from quartz-milonites indicate the Itapirapuã shear records a sinistral movement. The fabric of the plutons was studied by anisotropy of magnetic susceptibility (AMS) technique. Forty sites (300 specimens) were sampled at the Patrimônio Santo Antônio granite, 7 sites (48 specimens) at São Domingos, 9 sites (67 specimens) at Ouro Verde and 14 sites (92 specimens) at Santa Rita granite. The mean of magnetic susceptibility (k) is higher in Patrimônio Santo Antônio granite (k = 23,29 x \'10 POT.-3\' SI) and lower in the granites of Santa Rita (k = 11,85 mSI), São Domingos (k = 7,43 mSI) and Ouro Verde (k = 7,46 mSI). In contrast the magnetic anisotropy (P) is lower in the Patrimônio Santo Antônio granite (P = 1,09 ± 0,04) and higher in the granites São Domingos (P = 1,21 ± 0,09), Ouro Verde (P = 1,19 ± 0,07) and Santa Rita (P = 1,23 ± 0,11). Thermomagnetic and Isothermal Remanent Magnetization (IRM) studies show that Ti-poor magnetite is the principal carrier of rock magnetic properties but that includes minor contributions of Ti-hematite. Iron oxides are frequently associated with titanite, biotite and amphibole. Microstructures are typically magmatic, except for Santa Rita granite which shows post-magmatic recrystallized microstructures. The magnetic foliation of granitic plutons dips smooth to moderately and for the Patrimônio Santo Antônio body it exhibits a typical dome pattern. The subhorizontal magnetic lineation strikes NNW-SSE parallel to regional folding axe of the metasedimentary rocks. This feature shows that the granites are syntectonic to a deformation event apparently connected to NE-trending transcurrent shears. The occurrence of a foliation dome in the Patrimônio Santo Antônio pluton and prolate magnetic ellipsoids in São Domingos pluton suggest that the NNW-trending structures includes, besides a strike-slip shear fabric, a component of extension that probably assisted the emplacement of the plutons. A U-Pb (SHRIMP) determination in the Patrimônio Santo Antônio zircons have produced a concordia age of 589 ± 6 Ma attributed to the crystallization of the granite. These results indicate that in the latest stages of the development of the Cunhaporanga Intrusive Suite the Apiaí Domain was submitted to a regional strain field recording transcurrent simple shear and extension.

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30

Chater, Rabah. "Etude des antimonites MeSb 2 O 4 à basse température : évolution structurale, thermodynamique, propriétés élastiques et magnétiques anisotropes ; modélisation." Paris 6, 1986. http://www.theses.fr/1986PA066219.

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Etude par diffraction des RX et de neutrons, spectroscopie Raman et IR, chaleur massique, susceptibilité magnétique des antimonites (MNNifezn)sb2o4. Interprétation quantitative des anomalies de dilatation liées à Tltn dans le cas des composés de Ma et Fe. Définition d'un champ de force cohérent avec un potentiel de paires simplifié.

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31

Wack, Michael Richard. "Anisotropy of magnetic remanence." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-145717.

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32

Eisenbach, Markus. "Magnetic anisotropy in nanostructures." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364862.

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33

MUSCAS, GIUSEPPE. "Tuning the magnetic anisotropy in nanostructured magnetic oxides." Doctoral thesis, Università degli Studi di Cagliari, 2015. http://hdl.handle.net/11584/266794.

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Among nanostructured magnetic materials, nanoparticles (NPs) are unique complex physical objects: in these systems a multidomain organization is energetically unfavorable and single-magnetic-domain particles are formed, each one with a huge magnetic moment with comparison to that of single atoms, thus they are often named “supermoment”. The attractive performance of magnetic NPs based materials are appealing for several technological fields ranging from nanomedicine to high-density magneto recording. Thus, understanding the physics of magnetic nanoparticles and controlling their magnetic properties represent hot topics not only for fundamental studies but also for technological applications. The magnetic behavior of such entities is related to the reversal of their magnetization; this can be a thermal or a field activated transition, which is characterized by an energy barrier defined as a magnetic anisotropy energy (MAE), which is influenced by several parameters. Thus, the tuning of the magnetic properties of nanoparticles means control of the MAE. In this work it will be discussed how to tune the MAE at the nanoscale showing the main parameters that can influence the anisotropy itself. It will be investigated the role of particle volume in the effective anisotropy, and its correlation with the surface contribution, exploring its strong effect with particle size below 10 nm. In this framework it will be investigated the role of organic coating, underlining its ability to reduce the magnetic disorder arising from the broken symmetry at particles surface. In addition, in nanoparticle ensemble, the MAE may differ from one particle to another due to particles size and shape distributions. Thus it will be defined a detailed statistical analysis of particles’ morphology, leading to the development of a new instrument to analyze particles morphology, called “aspect maps”. The relation between the physical chemical structures of nanoparticles will be investigated on nickel doped cobalt ferrite samples, demonstrating how to tune the MAE by chemical composition, i.e., controlling magnetocrystalline anisotropy. Furthermore it will be analyzed the evolution of interparticles interactions with respect single particle magnetic anisotropy by means of a modified random anisotropy model. The last part of this work will deal with the design of novel nanostructured composites. La0.67Ca0.33MnO3 and CoFe2O4 will be combined using two different structures, which can be easily extent to other materials, to improve their magnetic interactions in order to obtain tunable magnetotrasport proprieties of the final composites.

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34

Bali, R. "Exchange anisotropy in magnetic thin films." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596311.

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I have studied Exchange Bias in epitaxial α-Fe₂O₃ and polycrystalline FeMn and CoMn antiferromagnets coupled to the ferromagnet Permalloy (Ni₈₁Fe₁₉). Despite the nominal magnetocrystalline anisotropy of Permalloy, surface features such as vicinal steps and roughness induced strong uniaxial anisotropy. Exchange coupling with epitaxial α-Fe₂O₃ led to a biaxial anisotropy component in the ferromagnet. Anisotropy axes of the biaxial component remained fixed despite applying magnetic field at elevated temperatures. The magnitude of biaxial anisotropy varied with every temperature cycle, providing implicit evidence of domains in the antiferromagnet. In polycrystalline systems, uniaxial anisotropy of the ferromagnet set-up during growth competes with exchange anisotropy. By setting up an AF/F/AF trilayer, magnetic field cooling allowed control of the net anisotropy. These findings demonstrate that the two crucial factors that impact exchange biased thin films are (1) uniaxial anisotropies in the ferromagnet from surface and growth conditions and (2) exchange coupling with domains in the antiferromagnet. Competing effect of these two factors is the key to understanding any exchange coupled system.

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35

Chilton, Nicholas Frederick. "Magnetic anisotropy of transition metal complexes." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/magnetic-anisotropy-of-transition-metal-complexes(64b34057-8a7a-44db-a89a-22a233fdefb5).html.

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The study of magnetic anisotropy in molecular systems permeates the physical sciences and finds application in areas as diverse as biomedical imaging and quantum information processing. The ability to understand and subsequently to design improved agents requires a detailed knowledge of their fundamental operation. This work outlines the background theory of the electronic structure of magnetic molecules and provides examples, for elements across the Periodic Table, of how it may be employed to aid in the understanding of magnetically anisotropic molecules. The magnetic anisotropies of a series of dimetallic NiII2 complexes and a RuIII2MnII triangle are determined through multi-frequency Electron Paramagnetic Resonance (EPR) spectroscopy and ab initio calculations. The magnetic anisotropy of the former is found to be on the same order of magnitude as the isotropic exchange interactions, while that of the latter is found to be caused by large antisymmetric exchange interactions involving the RuIII ions. An intuitive electrostatic strategy for the prediction of the magnetic anisotropy of DyIII complexes is presented, allowing facile determination of magnetic anisotropy for low symmetry molecules. Through the presentation of the first near-linear pseudo-two-coordinate 4f-block complex, a new family of DyIII complexes with unprecedented Single Molecule Magnet (SMM) properties is proposed. Design criteria for such species are elucidated and show that in general any two-coordinate complex of DyIII is an attractive synthetic target. The exchange interaction between two DyIII ions is directly measured with multi-frequency EPR spectroscopy, explaining the quenching of the slow magnetic relaxation in the pure species compared to the SMM properties of the diluted form. The interpretation of this complex system was achieved with supporting ab initio calculations.

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36

Rafique, Sadia. "Magnetic Anisotropy of Fe1-xGax Alloys." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/133.

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Thesis (M.S.) -- University of Maryland, College Park, 2003.
Thesis research directed by: Dept. of Materials Science and Nuclear Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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37

Short, Geoffrey. "Study of magnetic anisotropy by Magnetic Circular X-ray Dichroism." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310961.

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38

Chen, Way Cherng. "Magnetic susceptibility-based white matter magnetic resonance imaging techniques." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:7272b7e6-1fb9-4a1b-a71f-2ce5dfe93fde.

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Gradient echo (GRE) imaging, a magnetic resonance imaging (MRI) technique that is sensitive to changes in the magnetic susceptibility property of tissues, has recently revealed significant signal heterogeneity in white matter (WM) at high magnetic field B0 ≥ 3T. Various aspects of the underlying white matter microstructure have been linked to the observed contrast between white matter regions. This thesis investigates the origins of the observed differences in GRE signal behaviour. We proposed an explicit multi-compartmental model of WM that incorporates realistic representation of the geometry and magnetic susceptibility of the underlying microstructure that can be used to study the effects of WM microstructural changes on GRE signal characteristics. In particular, we looked at the apparent transverse relaxation rate (R2*) and the resonance frequency, as well as their respective deviations from mono-exponential decay and linear phase evolution. Next, we investigated the effect of WM fiber orientation on GRE signal using healthy human volunteers at 3T by correlating the GRE signal from different WM regions with WM fiber orientation information. Using literature-based parameters, we demonstrated that the geometric model predicted similar trends. Lastly, we studied the effect of myelin on GRE signal using a cuprizone mouse model at 7T . An ex vivo study was used to correlate GRE signal in fixed mouse brain with normalized myelin stain intensity. Simulated GRE signal from hypothetical scenarios of demyelination were then compared with the experimental results. R2* and resonance frequency were then used in an in vivo longitudinal study to track myelin changes during demyelination and subsequent remyelination.

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39

Zhang, Hongbin. "Relativistic Density Functional Treatment of Magnetic Anisotropy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25132.

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Spin-orbit coupling (SOC) reduces the spatial symmetry of ferromagnetic solids. That is, the physical properties of ferromagnetic materials are anisotropic, depending on the magnetization direction. In this thesis, by means of numerical calculations with full-relativistic density functional theory, we studied two kinds of physical properties: surface magnetic anisotropy energy (MAE) and anisotropic thermoelectric power due to Lifshitz transitions. After a short introduction to the full-relativistic density functional theory in Chapter 2, the MAE of ferromagnetic thin films is studied in Chapter 3. For such systems, separation of different contributions, such as bulk magnetocrystalline anisotropy (MCA) energy, shape anisotropy energy, and surface/interface anisotropy energy, is crucial to gain better understanding of experiments. By fitting our calculating results for thick slabs to a phenomenological model, reliable surface MAE could be obtained. Following this idea, we have studied the MAE of Co slabs with different geometries, focusing on the effects of orbital polarization correction (OPC). We found that the surface anisotropy is mainly determined by the geometry. While OPC gives better results of orbital moments, it overestimates the MAE. In the second part of Chapter3, the effects of electric fields on the MAE of L10 ferromagnetic thin films are studied. Using a simple model to simulate the electric field, our calculations are in good agreement with previous experimental results. We predicted that for CoPt, even larger effects exist. Moreover, we found that it is the amount of screening charge that determines the magnetoelectric coupling effects. This gives us some clue about how to achieve electric field control of magnetization direction. In Chapter 4, Lifshitz transitions in L10 FePt caused by a canted magnetic field are studied. We found several Lifshitz transitions in ordered FePt with tiny features in DOS. Using a two-band model, it is demonstrated that at such transitions, the singular behaviour of kinetic properties is due to the interband scattering, and the singularity itself is proportional to the derivative of the singular DOS. For FePt, such singularity will be smeared into anomaly by chemical disorder. Using CPA, we studied the effects of energy level broadening for the critical bands in FePt. We found that for experimentally available FePt thin films, Lifshitz transitions would induce up to a 3% increase of thermopower as the magnetization is rotated from the easy axis to the hard axis
Spin-Bahn-Kopplung reduziert die Symmetrie ferromagnetischer Festkörper. Das bedeutet, dass die physikalischen Eigenschaften ferromagnetischer Stoffe anisotrop bezüglich der Magnetisierungsrichtung sind. In dieser Dissertation werden mittels numerischer voll-relativistischer Dichtefunktional-Rechnungen zwei Arten physikalischer Eigenschaften untersucht: magnetische Oberflächen-Anisotropieenergie (MAE) und anisotrope Thermokraft durch Lifshitz-Übergänge. Nach einer kurzen Einführung in die relativistische Dichtefunktional-Theorie in Kapitel 2 wird in Kapitel 3 die MAE ferromagnetischer dünner Filme untersucht. In diesen Systemen ist es für ein Verständnis experimenteller Ergebnisse wichtig, verschiedene Beiträge zu separieren: Volumenanteil der magnetokristallinen Anisotropie (MCA), Formanistropie und Oberflächen bzw. Grenzflächenanisotropie. Durch Anpassen berechneter Daten für dicke Schichten an ein phänomenologisches Modell konnten verlässliche Oberflächen Anisotropien erhalten werden. In dieser Weise wurde die MAE von Co- Schichten mit unterschiedlichen Geometrien untersucht, wobei der Einfluss von Orbitalpolarisations-Korrekturen (OPC) im Vordergrund stand. Es wurde gefunden, dass die Oberflächenanisotropie hauptsächlich von der Geometrie bestimmt wird. Während OPC bessere Ergebnisse für die Orbitalmomente liefert, wird die MAE überschätzt. Im zweiten Teil von Kapitel 3 wird der Einfluss elektrischer Felder auf die MAE von dünnen ferromagnetischen Filmen mit L10-Struktur untersucht. Unter Verwendung eines einfachen Modells zur Simulation des elektrischen Feldes liefern die Rechnungen gute Übereinstimmung mit vorliegenden experimentellen Ergebnissen. Es wird vorhergesagt, dass für CoPt ein noch größerer Effekt existiert. Weiterhin wurde gefunden, dass die magnetoelektrische Kopplung von der Größe der Abschirmladung bestimmt wird. Dies ist eine wichtige Einsicht, um die Magnetisierungsrichtung durch ein elektrisches Feld kontrollieren zu können. In Kapitel 4 werden Lifshitz-Übergänge untersucht, die ein gekantetes Magnetfeld hervorruft. Es wurden mehrere Lifshitz-Übergänge in geordnetem FePt gefunden, welche kleine Anomalien in der Zustandsdichte hervorrufen. Mit Hilfe eines Zweiband-Modells wird gezeigt, dass an solchen Übergängen das singuläre Verhalten kinetischer Eigenschaften durch Interband- Streuung verursacht wird und dass die Singularität proportional zur Ableitung der singulären Zustandsdichte ist. In FePt wird durch chemische Unordnung diese Singularität zu einer Anomalie verschmiert. Der Einfluss einer Verbreiterung der Energieniveaus der kritischen Bänder in FePt wurde mittels CPA untersucht. Es wurde gefunden, dass in experimentell verfügbaren dünnen FePt-Filmen Lifshitz-Übergänge bis zu 3% Erhöhung der Thermokraft erzeugen, wenn die Magnetisierung von der leichten in die harte Richtung gedreht wird

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Rozatian, Amir Sayid Hassan. "Anisotropy and interface structure in magnetic multilayers." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2825/.

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It is believed that the interfacial structure can significantly affect the magnetic properties of magnetic multilayer thin films. X-ray scattering techniques provide a powerful method with which to study the bulk and interface morphology in these systems, and are therefore crucial in developing an understanding of the dominant factors influencing the magnitude of the perpendicular magnetic anisotropy (PMA).The inter-relation between magnetic and structural properties of a series of magnetic multilayer thin films is investigated. Magnetometry measurements on a series of Fe/Au multilayers showed that some samples exhibited in-plane magnetization. X-ray data and simulations showed that the interface roughness was high in these samples. However, the formation and propagation of uncorrelated roughness followed a systematic trend for surface growth. On the other hand, x-ray data and simulations for a single 100-bilayer sample showed that the interfaces are much better defined with significantly lower roughness. This was the only sample to show perpendicular anisotropy supposing the suggestion that the absence of PMA in all other samples is associated with high interface roughness. Magnetometry measurements of the PMA in Co/Pt multilayers show an increase in effective anisotropy at about 15 bilayers. X-ray data showed that the roughness of the interfaces was correlated in all samples and that the interfaces were sharp with no detectable interdiffusion. No systematic trend in roughness or crystallographic texture is detected with increasing bilayer repeat X-ray measurements on four series of Co/Pd multilayers show interface roughness independent of bilayer repeat number. For Co/Pt, the in-plane correlation length was independent of bilayer number while for Co/Pd and Fe/Au it increased. A saturation of the in-plane correlation length for the Au/Fe system where island growth of the Au occurs was observed. The out-of-plane correlation length increased with bilayer repeat for Co/Pt and Co/Pd. The interfaces in samples with higher PMA had a fractal parameter close to unity.

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Shirtcliffe, James Leslie. "Electrodeposited alloy nanostructures with tuneable magnetic anisotropy." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.730831.

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Vopsaroiu, Marian. "Anisotropy and texture studies in magnetic media." Thesis, University of Central Lancashire, 2002. http://clok.uclan.ac.uk/20302/.

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The rapid development of magnetic materials for recording media applications increased the demands for new and more precise experimental investigation techniques. In respect with these demands, this project is focused on experimental analyses of advanced particulate media and magnetic thin film samples. A new extended rotational remanence technique for anisotropy field measurements was developed. The technique is suitable for samples that contain aligned or partially aligned particles and provides both: in-plane anisotropy field distributions and the in-plane anisotropy field. This technique was also extended to out-of-plane anisotropy field measurements. Rotational hysteresis was introduced as an alternative method for anisotropy field measurements. This applies well in the case of samples without texture or samples having very small magnetic moment (i.e. thin films). The two techniques for anisotropy field measurement compare well and the experimental results were interpreted in terms of inter-particles interactions. Two measurement methods for determination of the demagnetizing field acting perpendicular to a sample plane were also developed. The first method is based on the in-plane and out-of-plane anisotropy field determination using an extended rotational remanence technique. The second method can provide the demagnetizing field starting from in-plane and out-of-plane transverse hysteresis loops. Comparison between the results from the two methods showed good agreement. Furthermore, the demagnetizing field values were used to calculate the magnetic coating thickness, so the two methods provide a non-destructive method for magnetic thickness measurements in film samples. The in-plane easy axis distribution (EAD) was experimentally determined using vector VSM techniques. Correlations between in-plane tape texture and magnetic thickness were obtained for a series of advanced MP tapes. A theoretical approach was used in order to relate the orientation ratio to EAD. The out-of-plane EAD was derived from numerical calculations. The out-of-plane distribution also showed a variation with the magnetic thickness. In addition, the microstructure and particle morphology of the advanced MP tapes, as well as the out-of-plane component of magnetization, have been investigated using Mossbauer Spectroscopy. Finally, 3D - EAD maps were produced. All VSM experiments were fully computer controlled and the routines were designed in the LabView environment as part of this project.

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Cubukcu, Murat. "Manipulation of magnetic anisotropy in ferromagnetic semiconductors." Paris 6, 2010. http://www.theses.fr/2010PA066159.

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Cette thèse présente une étude de l’anisotropie magnétique de semiconducteurs ferromagnétiques en couches minces et du couplage magnétique dans des bicouches formées à partir de ces matériaux et de métaux ferromagnétiques. Je me suis focalisé sur deux systèmes distincts : des films minces de l’alliage quaternaire GaMnAsP et des bicouches : MnAs/GaMnAs. Dans ces systèmes, j’ai étudié l’influence sur les anisotropies magnétiques d’une part, de la déformation biaxiale induite par le désaccord de maille avec le substrat et d’autre part, de la concentration en trous. Ces études ont été menées principalement par résonance ferromagnétique, mesures d’aimantation par SQUID, ainsi que grâce à des mesures de transport et de diffraction de rayons X à haute résolution. Deux séries de films de GaMnAsP caractérisées par des concentrations en Mn de 7 et 10% ont été étudiées. Pour chaque série, la concentration en P a été variée sur une large gamme de 0 à 20%. Les forts dopages en P sont intéressants car le régime de conduction peut changer, passant de métallique à bande d’impuretés. Ceci induit de profondes modifications de tous les paramètres magnétiques pertinents. Nous avons étudié les variations d’anisotropie magnétique avec la concentration en P. Une réorientation de l’aimantation avec la température a pu être mise en évidence pour une concentration 6% P. La relaxation de l’aimantation de ces systèmes a été étudiée via le facteur de Gilbert. Des mesures de RFM à haute fréquence ont permis d’étudier l’anisotropie magnétique de films de MnAs épitaxiés sur (111) et (100)GaAs. Un couplage d’échange ferromagnétique est mis en évidence pour les bicouches MnAs/GaMnAs

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Soldatov, Ivan. "Thermoelectric effects and anisotropy in magnetic ﬁlms." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-197529.

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It was the purpose of this thesis to contribute to a better understanding of spin caloritronic phenomena and thermoelectric eﬀects as well as the anisotropy of magnetic thin ﬁlms. Mostly this work was motivated by the recent discovery of the spin Seebeck eﬀect (SSE) in Japan: a generation of a pure spin current across the interface between magnetic|nonmagnetic materials upon application of the temperature gradient along (transversal SSE) or across (longitudinal SSE) the interface. As the experimental conﬁguration for the TSSE involves the heat ﬂows, special care to spurious temperature gradients has to be taken. Semiconducting GaMnAs and insulating yttrium iron garnet (YIG) magnetic thin ﬁlms were investigated. As nonmagnetic material platinum was chosen, providing also the opportunity to detect pure spin currents via the spin Hall eﬀect (SPHE) in it. Starting with the measurement of in-plane voltages, transverse to the in-plane temperature gradient and measured along the platinum stripes, by sweeping the external magnetic ﬁeld at diﬀerent in-plane directions (TSSE geometry), symmetric and asymmetric contributions were observed in both, the GaAs/GaMnAs/Pt and GaAs/GaMnAs systems. The former was clearly attributed to the planar Nernst eﬀect, arising from an in-plane temperature gradient along the sample, while the latter was shown to be result of the anomalous Nernst eﬀect (ANE) caused by spurious out-of-plane temperature gradients. Using the ANE constant that was measured upon deliberately applying an out-of-plane temperature gradient, it was estimated that a rather small temperature drop of ΔT z ≈ 12 nK across the 200 nm magnetic ﬁlm thickness can be responsible for the appearance of spurious ANE signals, leading to the asymmetry of the thermovoltages registered in the PNE/TSSE conﬁguration. Thus, the TSSE if it exists at all in the GaMnAs sample, is very likely to be negligible. The transport measurements in the insulating YIG sample in TSSE/PNE conﬁguration demonstrated no ﬁeld dependencies, supporting the idea that the signals in the semiconducting GaMnAs ﬁlm originated not from the TSSE, but rather from the conventional ANE. The voltages in ANE/LSSE conﬁguration the characteristic LSSE signals were observed. This thesis is also devoted to the magnetic anisotropy investigation in GaMnAs thin ﬁlm by applying wide-ﬁeld Kerr microscopy simultaneously to galvanomagnetic measurements. Upon sweeping the magnetic ﬁeld the development of magnetic domains was traced: at low temperatures (5 K) the sample exhibits a clear two-fold switching of magnetization, while at higher temperatures (above 20 K) only a one-step switching was detected, indicating a strong temperature dependence of the magnetic anisotropy. The same behavior was derived from the transport measurements in the PHE conﬁguration. Rotating the ﬁeld in the plane of the thin ﬁlm and analyzing the resulting angle dependencies of the transversal voltage, we obtained the anisotropy constants K u and K c . The temperature dependence of the K u / K c -ratio showed a gradual substitution of the cubic anisotropy, prevailing at low temperatures, by a uniaxial one with rising temperature. For the purpose of the magneto-optical investigation and in-depth analysis of the magnetic anisotropy, within the frame of this thesis a new hardware and software realization for quantitative Kerr microscopy was developed. The principles of such a technique were formulated already years ago by Rave et al, but the experimental realization was limited to materials with in-plane surface magnetization and static domain imaging due to the manual adjustment of the microscope sensitivity. The realization of a separation of in-plane|out-of-plane magnetic contrast, suggested in this thesis, disposes those complications and improves the method, providing the opportunity for a simultaneous measurement of both components of magnetization in an automatic regime and, thus, allowing the quantitative analysis of the magnetization reorientation processes in magnetic media. This technique was successfully applied to the quantitative investigation of the magnetic domain structure in GaMnAs ﬁlm, and was also demonstrated on a number of other materials, including a permalloy (Ni 81 Fe 19 ) patterned ﬁlm element and the separation of the in-plane and out-of-plane components of magnetic contrast in sintered NdFeB polycrystals. In summary, this work contributes to a deeper understanding of the contribution of the conventional thermoelectric eﬀects to the exploding ﬁeld of spin caloritronic. It points out that thermoelectric phenomena have to be treated with care and that magnetic anisotropy and its temperature dependence have to be considered in any analysis of spin caloritronic phenomena. The thesis extends the existing methods of investigating magnetic anisotropy of magnetic ﬁlms by introducing a novel technical realization of quantitative Kerr microscopy.

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Fard, Samad Moemen Bellah. "Modelling anisotropy in electrotechnical steels." Thesis, Cardiff University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263551.

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Lamarche, Geoffroy. "ANALYSE MICROSTRUCTURALE ET FABRIQUE MAGNÉTIQUE. L'EXEMPLE DES CALCSCHISTES ET DES FLYSCHS DE LA ZONE DAUPHINOISE. {ALPES FRANÇAISES}." Phd thesis, Grenoble 1, 1987. http://tel.archives-ouvertes.fr/tel-00452022.

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La susceptibilité magnétique peut servir dans les études géologiques comme un indicateur de l'évolution pétrologique et structurale des roches. Cela nécessite une démarche particulière qui est développée ici, sur les roches sédimentaires déformées: les trois points suivants sont la base de cette étude. Les mécanismes de déformation et les différentes structure géologiques résultantes. L'origine de la susceptibiiité magnétique et de son anisotropie (A.S.M.) : minéralogie magnétique et pétrofabrique des minéraux anisotropes. L'utilisation de méthodes géométriques pour analyser les directions de l'ASM, notamment dans les cas d'interférences de structures. Dans les calcschistes du Jurassique et les flyschs éocènes de la zone dauphinoise la susceptibilité magnétique est due au paramagnétisme des phyllosilicates, qui constitue la matrice, et au ferromagnétisme de la magnétite. L'A.S.M. se corrèle bien aux structures de déformation: la foliation magnétique - c'est·à-dire le plan perpendiculaire à la susceptibilité magnétique minimale, K3 - est systématiquement confondue avec la stratification ou la schistosité. La linéation magnétique (susceptibilité maximum K1) a tendance à indiquer l'intersection stratification/schistosité dans les niveaux marneux, riches en phyllosilicates, et l'étirement dans le sens du transport dans les niveaux plus calcaires, reiativement plus riche en magnétite. Il est possible à partir de l'A.S .M. d'aborder les problèmes d'interactions des structures sur les propriétés magnétiques directionnelles et de déterminer les orientations tectoniques en l'absence de marqueurs structuraux. Le métamorphisme alpin peut·être mis évidence par la décroissance de la susceptibilité lors du passage dans l'épizone. On discute les possibilités d'estimer le taux de déformation grâce à l'A.S.M., et on proposera, enfin, une méthode générale d'étude structurale au moyen de l'A.S.M ..

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Satter, Md Abdus. "A theory for dilute magnetic alloys : the origin of magnetic anisotropy." Thesis, University of Warwick, 1989. http://wrap.warwick.ac.uk/101517/.

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In this thesis, a formalism for studying the anisotropic interaction between two substitutional magnetic impurities and the magnetic anisotropic effect in a dilute noble metal-transition metal magnetic alloy has been developed from relativistic scattering theory. The theoretical development and the computational techniques of this formalism are based on relativistic spin-polarised scattering theory and relativistic band structure frameworks. For studying the magnetic anisotropic effect a convenient ‘working’ frame of reference with its axes oriented along the fee crystal axes is set up. This formalism is applied to study the situation for two Fe impurities in both paramagnetic Au (heavy) and Cu hosts. For AuFe dilute alloy, the two impurity site interaction as a function of separation is not oscillatory and the anisotropic effect is found to be less than the two site interaction itself only by an order of magnitude. Apart from the anisotropic coupling of the two impurity spins to the separation vector, for the first time, another weak anisotropic coupling to the crystal axes is also contained in the two site interaction. These anisotropic effects are the results of the relativistic spin-orbit interaction which are incorporated into the formalism.

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Vannette, Matthew Dano. "Dynamic magnetic susceptibility of systems with long-range magnetic order." [Ames, Iowa : Iowa State University], 2009.

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Ribow, Mirko [Verfasser]. "Voltage control of magnetic anisotropy in ultrathin epitaxial magnetic layers / Mirko Ribow." Halle, 2018. http://d-nb.info/1162892781/34.

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Kugler, Zoe [Verfasser]. "Perpendicular anisotropy in magnetic tunnel junctions / Zoe Kugler." Bielefeld : Universitätsbibliothek Bielefeld, Hochschulschriften, 2012. http://d-nb.info/1023862891/34.

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Dissertations / Theses on the topic 'Anisotropy of magnetic susceptibility'

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