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Dissertations / Theses on the topic 'Atomic magnetometry'
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1
Sataline, Christopher J. "Remotely-sensed atomic magnetometry." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12213.
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Thesis (M.S.)--Boston University<br>Coherent population trapping (CPT) effects can be realized with frequency mod- ulated lasers and compact vapor cells of alkali metals such as Rubidium-87. Using these optical resonances, one can readily measure the hyperfine separation of this three-level atom. In the presence of a magnetic field, the Zeeman effect causes magnetic sublevels of these hyperfine ground states to split; the frequency of such splitting can be measured in an ensemble of Rubidium atoms with the magnetometer we have constructed. While other groups have constructed magnetometers based on these effects, none to our knowledge have investigated the capability to measure magnetic fields remotely. Most atomic-optical magnetometers,colocate the transmit and receive optical system with the vapor cell itself or require fiber optics at the location of the cell; our free-space technique with a reflective geometry lends itself to measurement at distances greater than could be achieved with those methods. We have developed a laboratory FM laser spectrometer that interrogates CPT resonances to measure magnetic fields with the vapor cell not necessarily co-located with the spectrometer. Its intrinsic linewidth (in the presence of transit-time broadening) is less than 30 kilohertz, which allows measurements on the order of 2 microtesla. We present results concerning the accuracy of the magnetometer at about one meter of standoff distance, and describe considerations for measurements at longer distances.
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Chisholm, Nicholas Edward Kennedy. "Single spin magnetometry with nitrogen-vacancy centers in diamond." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467355.
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The nitrogen-vacancy (NV) center in diamond is a solid-state point defect with an electronic spin that has accessible quantum mechanical properties. At room temperature, the electronic ground state sub-levels of the NV center can be initialized and read out using optical pumping, as well as coherently controlled using microwave frequency fields. This thesis focuses on using the spin state of the NV center for highly-sensitive magnetometry under ambient conditions. In particular, when the diamond surface is properly prepared, we demonstrate that NV centers can be used to measure the magnetic fluctuations stemming from individual molecules and ions attached or adsorbed to the surface.
This thesis begins by introducing the physical and electronic structure of the NV center at room temperature, followed by the fundamental measurements that allow us to use the NV center as a sensitive magnetometer. Combining our sensitive NV center magnetometer with techniques from chemistry and atomic force microscopy (AFM), we demonstrate the all-optical detection of a single-molecule electron spin at room temperature. Finally, we discuss the time-resolved detection of individual electron spins adsorbing onto the surface of nano-diamonds. By extending our techniques to nano-diamonds, we move closer towards \textit{in vitro} magnetic field sensing that could be pivotal for better disease diagnosis and drug development.<br>Engineering and Applied Sciences - Applied Physics
3
Chang, Kevin Kai. "Custom built atomic force microscope for nitrogen-vacancy diamond magnetometry." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68549.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 27).<br>The nitrogen-vacancy (N-V) center in diamonds have the potential to be an ultra-sensitive magnetic field sensor that is capable of detecting single spins. Implementing this sensor for general and nontransparent samples is not trivial. For N-V centers to be a useful probe, a way of positioning the NV center with nanometer accuracy while simultaneously measuring its fluorescence is needed. Here, a method of using N-V centers as magnetometer probes by combining this sensor with Atomic Force Microscopy (AFM) is described. A custom AFM was built that allows optical monitoring of the cantilever tip and collection of fluorescence with a high-NA objective from the same side. The AFM has a large open bottom and top and thus provides dual optical access. The motion of the cantilever is measured by optical beam deflection so that a wide range of commercial cantilevers can be used. The AFM and the confocal microscope objective can be locked in position while a piezoelectric stage allows raster scanning of the substrate.<br>by Kevin Kai Chang.<br>S.M.
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Venturelli, Michela. "Ultra-cold atomic magnetometry : realisation and test of a 87Rb BEC for high-sensitivity magnetic field measurements." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10055887/.
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The development of an experimental apparatus to produce Bose-Einstein condensates (BECs) of 87Rb atoms and their application to magnetometry are discussed. Optical detection of atomic Larmor precession is a widely explored method for high-sensitivity measurements of magnetic fields. In this context, short laser/atom interaction time, atomic thermal diffusion and decoherence effects are among the main limitations. In this thesis, we overcome such problems by using spin-polarised 87Rb ultra-cold atoms as the sensing element. After the atoms are polarised, a resonant pulse of radio-frequency excites Larmor precession, which is sensitive to external magnetic fields. By measuring the perturbations of the radio-frequency induced spin precession, information on the magnetic fields of interest. This is achieved by monitoring the polarisation plane’s rotation of a linearly polarised resonant laser probe. In the first part of this thesis, the building and optimisation of a laser-cooling set up to obtain a BEC in a hybrid trap is reported. In order to achieve the Phase Space Density (PSD) required for BEC, several different stages of trapping and cooling are necessary. Each phase has been implemented and optimised. The first step consists in the magneto-optical trap (MOT). Here a velocity dependent damping force and a spatially dependent confining force give the largest changes in PSD. Then atoms are loaded into a hybrid trap obtained by overlapping a quadrupole magnetic potential and a far detuned optical crossed dipole trap. The final stage for the condensation consists of forced evaporative cooling, both via magnetic and optical evaporation. In the second part of the thesis, a general overview of the principles of optical atomic magnetometry is provided and the advantages of using ultra-cold atoms with respect to conventional thermal vapours are discussed. The implementation, operation and a preliminary characterisation of the ultra-cold atom magnetometer are described along with the preliminary results collected. Finally, a plan for future improvements of its sensitivity is presented.
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Shields, Brendan John. "Diamond platforms for nanoscale photonics and metrology." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11638.
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Observing and controlling solid state quantum systems is an area of intense research in quantum science today. Such systems offer the natural advantage of being bound into a solid device, eliminating the need for laser cooling and trapping of atoms in free space. These solid state "atoms" can interface directly with photonic channels designed to efficiently couple into larger networks of interacting quantum systems. With all of the tools of semiconductor fabrication technology available, the idea of scalable, chip-based quantum networks is a tantalizing prospect.<br>Physics
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Piccolomo, Savino. "Chip-scale atomic magnetometer." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27528.
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Kermaidic, Yoann. "Mesure du moment dipolaire électrique du neutron : analyse de données et développement autour du ¹⁹⁹Hg." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY055/document.
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Un moment dipolaire électrique permanent (EDM) est une propriété fondamentale des systèmes simples comme par exemple l'électron, les atomes/molécules ou le neutron dont l'existence est prédite par le Modèle Standard de la physique des particules (MS) mais qui n'a pas pour l'heure jamais été observée. Cette observable violant la symétrie CP offre la possibilité de relier la physique des particules à l'énigme cosmologique fondamentale de l'asymétrie baryonique de l'Univers observée de nos jours. Produire une telle asymétrie requiert de nouvelles sources/de nouveaux mécanismes de violation de CP, hors MS, qui peuvent être sondés de façon privilégiée par les recherches d'EDM. La sensibilité des expériences EDM actuelles se trouve des ordres de grandeurs au-dessus des prédictions du secteur faible du MS. L'absence de signal, après 60 ans de quête, détermine la limite supérieure la plus forte sur la violation de CP dans le secteur fort du MS et contraint l'espace des phases des modèles de nouvelle physique. A contrario, la mesure d'un EDM non nul dans les années à venir pourra s'interpréter comme le signal d'une physique au-delà du MS évoluant à l'échelle multi-TeV. Dans cette perspective envoûtante, de nombreux nouveaux projets de mesures des EDM ont vu le jour ces dernières années et d'importants efforts sont poursuivis auprès du neutron notamment. Ce manuscrit présente la recherche de l'EDM du neutron menée auprès de l'expérience la plus sensible à ce jour basée à l'Institut Paul Scherrer en Suisse<br>A permanent electric dipole moment (EDM) is a fundamental property of simple systems such as the electron, atoms/molecules or the neutron whose amplitude is expected to be non-zero within the Standard Model of particles physics (SM) but which has never been observed so far. This observable violating the CP symmetry offers the opportunity to link particle physics to the fundamental cosmological enigma of the observed baryon asymmetry of the Universe. Such an asymmetry requires new CP violation sources/mechanism beyond the SM, which can be best probed by EDM searches. The current EDM experiments sensitivity is order of magnitude above the weak SM sector predictions. Measuring a null EDM, after a 60 years quest, set the strongest upper limit on the CP violation in the strong SM sector and constrains the new physics models phase space. On the contrary, measuring a non-zero EDM in the coming years can be understood as a signal from physics beyond the SM evolving at a multi-TeV scale. In this haunting perspective, many new EDM projects raised in the last years and important efforts are pursued near the neutron in particular. This manuscript present the neutron EDM search near the most sensitive experiment running at the Paul Scherrer Institute in Switzerland
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Rajroop, Jenelle. "Radio-frequency atomic magnetometers : an analysis of interrogation regimes." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10050803/.
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An atomic magnetometer is a sensor which is used to measure a magnetic field through its interaction with the atomic sample. Significant research into atomic magnetometry has led to the development of very sensitive atomic sensors capable of matching the sensitivity of the most sensitive magnetometers, superconducting quantum interference devices (SQUIDs). Because SQUIDS require cryogenics to operate, atomic magnetometers provide a sensitive, yet low-cost alternative. They have found use in many areas such as medicine, security, explosives detection and fundamental physics research. One of the primary factors influencing sensitivity is the detuning of the probe beam from the resonant transitions of the atomic ground state. A caesium room temperature radio-frequency (rf) magnetometer is constructed and used to investigate the influence of the probe beam detuning on the magnetometer signal of the F = 3 and F = 4 ground states. The results of probing near and far from resonance revealed an off-resonant regime and two absorptive regimes. In the off-resonant regime, the atomic spins are unperturbed by the probe beam; it is a quantum non-demolition (QND) interaction. The two absorptive regimes, found when the probe beam is in the vicinity of either the 62S1 2 F = 3 → 6 2P3 2 F 0 = 2,3,4 or the 62S1 2 F = 4 → 6 2P3 2 F 0 = 3,4,5 transitions, is characterised as a non-QND interaction in which the probe beam influences the measurement. The sensitivity of the rf magnetometer is determined to be ≈ 1.98 fT/ √ Hz. In addition, the exploration of the relationship between the signal to noise ratio (SNR) and probe beam detuning revealed that the SNR is constant with detuning but the larger the detuning, the higher the probe beam power needs to be to reach the optimum SNR.
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Rutkowski, Jaroslaw. "Study and Realization of a Miniature Isotropic Helium Magnetometer." Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2005/document.
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Roccia, Stéphanie. "La co-magnétométrie mercure pour la mesure du moment électrique dipolaire du neutron : optimisation et application au test de l'invariance de Lorentz." Grenoble 1, 2009. https://theses.hal.science/tel-00440287.
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Cette thèse traite de la magnétométrie dans le cadre de la mesure du moment électrique dipolaire du neutron avec le spectromètre RAL/Sussex/ILL. En particulier, le co-magnétomètre mercure, pré-existant, a été modélisé et optimisé en vue de son utilisation pour les prochaines mesures au Paul Scherrer Institut (Villigen, Suisse) en 2010-2012. Sur la base de données prises à l'Institut Laue-Langevin (Grenoble, France), la complémentarité entre la magnétométrie externe césium et la co-magnétométrie mercure a été étudiée. Un tel système de double magnétométrie est unique. Cette étude débouche sur une méthode permettant un meilleur controle des erreurs systématiques liées au co-magnétomètre mercure et sur une nouvelle contrainte sur des couplages exotiques du neutron libre violant l'invariance de Lorentz<br>In this thesis, magnetometry is studied in the context of the neutron Electric Dipole Moment (nEDM) measurement with the RAL/Sussex/ILL spectrometer. In particular, the pre-existing mercury co-magnetometer has been modeled and optimized to be used in the next nEDM measurement at the Paul Scherrer Institut (Villigen Suisserland) in 2010-2012. Using data taken at the Institut Laue-Langevin (Grenoble, France), the complementarity between external cesium magnetometry and mercury co-magnetometry has been studied, bringing two results : - a best way to control systematics due to the co-magnetometer - a limit on the neutron anomalous couplings that violates Lorentz invariance
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Sturm, Michael [Verfasser], Peter [Akademischer Betreuer] Fierlinger, Peter [Gutachter] Fierlinger, and Lothar [Gutachter] Oberauer. "A highly drift stable and fully optical Cs atomic magnetometer for a new generation nEDM experiment / Michael Sturm ; Gutachter: Peter Fierlinger, Lothar Oberauer ; Betreuer: Peter Fierlinger." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/121217819X/34.
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Lieb, Gaëtan. "Magnétomètre atomique tout-optique pour applications géophysiques, spatiales et médicales." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC252.
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La mesure du champ magnétique terrestre avec des satellites réduits en volume –des cube-sats ou des nano-sats– requière de des magnétomètres à pompage optique de volume plus réduit et pouvant être opérés en gradiomètre sans diaphonie entre capteurs. Pour répondre à ce besoin, nous avons travaillé sur des architectures de magnétomètres atomiques tout-optiques. Dans ce manuscrit, nous présentons une architecture de magnétomètre scalaire tout-optique isotrope basée l’hélium-4 métastable pompé en alignement. Cette architecture repose sur la combinaison d’un champ magnétique radiofréquence créé optiquement par l’effet de light-shift vectoriel et d’une modulation de l’intensité du faisceau de pompe. Les premiers tests expérimentaux de cette configuration ont démontré l’existence d’un point de travail permettant l’opération isotrope. Les premières estimations de bruit et de justesse de cette configuration laissent espérer des performances équivalentes à celles obtenues sur les magnétomètres scalaires isotropes réalisés par le CEA-Leti pour la mission Swarm.Les architectures tout-optique apporteraient également une réponse à des besoins existants dans le domaine de l’imagerie magnétique médicale. En effet la mise en réseau des capteurs actuels entraine des problèmes de diaphonie entre magnétomètres voisins. Dans un deuxième volet de cette thèse nous nous sommes donc intéressés aux magnétomètres tout-optique dédiés à la mesure de champs magnétiques de faibles amplitudes. En explorant les configurations de magnétomètres Hanle basés sur l’alignement atomique, nous avons identifié un schéma qui permet d’avoir accès à deux composantes du champ magnétique en utilisant un seul accès optique à la cellule de gaz. Cette solution a été testée expérimentalement. Nous étudions théoriquement une extension de cette configuration qui permet de mesurer les trois composantes du champ magnétique en utilisant pour le pompage optique une lumière partiellement dépolarisée<br>The measurement of the Earth magnetic field, using satellites of reduced volume –so called cube-sats or nano-sats– requires optically pumped magnetometers of strongly reduced size that can be operated as gradiometers without crosstalk between different sensors. In order to fulfill these conditions we developed an architecture for all-optical magnetometers.In this work, we present an all-optical isotopic solution for a scalar helium-4 magnetometer based on atomic alignment. This architecture originates in the combination of an optically created radiofrequency magnetic field realized by a vector light-shift and of an intensity modulation of the pump light. The first experimental tests of this configuration proved the existence of a working point that allows isotropic operation. First estimations of noise and precision using this configuration give hope to obtain equivalent performance than that of scalar isotropic magnetometers that were realized by the CEA-Leti for the mission Swarm.Additionally, the all-optical architectures respond to the needs that exist in the field of medical magnetic imaging. In fact, building a matrix of commonly used sensors involves problems of cross-talk between proximate magnetometers. The second focus of this thesis lies on all-optical magnetometers designated for the measurement of magnetic fields with small amplitudes. Exploring the configurations of Hanle magnetometers that are based on atomic alignment, we identified a technique which gives access to two magnetic field components while using only one single optical access to the gas cell, a solution that was experimentally tested. We theoretically investigate an extension of this configuration that allows the measurement of all three components of the magnetic field, using a partially depolarized light as optical pump
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Revalee, Jason S. "Accessibility and The Potential of Bio-Physiological Systems Measuring Human Magnetic Fields to Inform Technology Devices." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1559057599496862.
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Urban, Jeffry Todd. "Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects." Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/836811-joXo6p/native/.
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Thesis (Ph.D.); Submitted to the University of California, Berkeley, CA (US); 21 Dec 2004.<br>Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--56768" Urban, Jeffry Todd. USDOE Director. Office of Science. Office of Basic Energy Sciences (US) 12/21/2004. Report is also available in paper and microfiche from NTIS.
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Muduli, Pranaba Kishor. "Ferromagnetic thin films of Fe and Fe 3 Si on low-symmetric GaAs(113)A substrates." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15473.
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In dieser Arbeit werden das Wachstum mittels Molekularstrahlepitaxie und die Eigenschaften der Ferromagneten Fe und Fe_3Si auf niedrig-symmetirschen GaAs(113)A-Substraten studiert. Drei wichtige Aspekte werden untersucht: (i) Wachstum und strukturelle Charakterisierung, (ii) magnetische Eigenschaften und (iii) Magnetotransporteigenschaften der Fe und Fe_3Si Schichten auf GaAs(113)A-Substraten. Das Wachstum der Fe- und Fe_3Si-Schichten wurde bei einer Wachstumstemperatur von = bzw. 250 °C optimiert. Bei diesen Wachstumstemperaturen zeigen die Schichten eine hohe Kristallperfektion und glatte Grenz- und Oberflächen analog zu [001]-orientierten Schichten. Weiterhin wurde die Stabilität der Fe_(3+x)Si_(1-x) Phase über einen weiten Kompositionsbereich innerhalb der Fe_3Si-Stoichiometry demonstriert. Die Abhängigkeit der magnetischen Anisotropie innerhalb der Schichtebene von der Schichtdicke weist zwei Bereiche auf: einen Beresich mit dominanter uniaxialer Anisotropie für Fe-Schichten = 70 MLs. Weiterhin wird eine magnetische Anisotropie senkrecht zur Schichtebene in sehr dünnen Schichten gefunden. Der Grenzflächenbeitrag sowohl der uniaxialen als auch der senkrechten Anisotropiekonstanten, die aus der Dickenabhängigkeit bestimmt wurden, sind unabhängig von der [113]-Orientierung und eine inhärente Eigenschaft der Fe/GaAs-Grenzfläche. Die anisotrope Bindungskonfiguration zwischen den Fe und den As- oder Ga-Atomen an der Grenzfläche wird als Ursache für die uniaxiale magnetische Anisotropie betrachtet. Die magnetische Anisotropie der Fe_3Si-Schichten auf GaAs(113)A-Substraten zeigt ein komplexe Abhängigkeit von der Wachstumsbedingungen und der Komposition der Schichten. In den Magnetotransportuntersuchungen tritt sowohl in Fe(113)- als auch in Fe_3Si(113)-Schichten eine antisymmetrische Komponente (ASC) im planaren Hall-Effekt (PHE) auf. Ein phänomenologisches Modell, dass auf der Kristallsymmetrie basiert, liefert ein gute Beschreibung sowohl der ASC im PHE als auch des symmetrischen, anisotropen Magnetowiderstandes. Das Modell zeigt, dass die beobachtete ASC als Hall-Effekt zweiter Ordnung beschreiben werden kann.<br>In this work, the molecular-beam epitaxial growth and properties of ferromagnets, namely Fe and Fe_3Si are studied on low-symmetric GaAs(113)A substrates. Three important aspects are investigated: (i) growth and structural characterization, (ii) magnetic properties, and (iii) magnetotransport properties of Fe and Fe_3Si films on GaAs(113)A substrates. The growth of Fe and Fe_3Si films is optimized at growth temperatures of 0 and 250 degree Celsius, respectively, where the layers exhibit high crystal quality and a smooth interface/surface similar to the [001]-oriented films. The stability of Fe_(3+x)Si_(1-x) phase over a range of composition around the Fe_3Si stoichiometry is also demonstrated. The evolution of the in-plane magnetic anisotropy with film thickness exhibits two regions: a uniaxial magnetic anisotropy (UMA) for Fe film thicknesses = 70 MLs. The existence of an out-of-plane perpendicular magnetic anisotropy is also detected in ultrathin Fe films. The interfacial contribution of both the uniaxial and the perpendicular anisotropy constants, derived from the thickness-dependent study, are found to be independent of the [113] orientation and are hence an inherent property of the Fe/GaAs interface. The origin of the UMA is attributed to anisotropic bonding between Fe and As or Ga at the interface, similarly to Fe/GaAs(001). The magnetic anisotropy in Fe_3Si on GaAs(113)A exhibits a complex dependence on the growth conditions and composition. Magnetotransport measurements of both Fe(113) and Fe_3Si(113) films shows the striking appearance of an antisymmetric component (ASC) in the planar Hall effect (PHE). A phenomenological model based on the symmetry of the crystal provides a good explanation to both the ASC in the PHE as well as the symmetric anisotropic magnetoresistance. The model shows that the observed ASC component can be ascribed to a second-order Hall effect.
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Diallo, Lindor. "Etude à l'échelle atomique de l'implantation du fer dans le carbure de silicium (SiC) : Elaboration d'un semiconducteur magnétique dilué à température ambiante." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR053.
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Ce travail de thèse porte sur l’étude du carbure de silicium, dopé avec du fer dans le but de réaliser un semi-conducteur magnétique dilué à température ambiante pour des applications à la spintronique. Le dopage en fer a été réalisé par implantation ionique de type multi-énergie (30 - 160 keV) à différentes fluences, conduisant à une concentration atomique constante de 2 % de 20 à 100 nm. Il a été suivi d’un recuit à haute température dans le but d’homogénéiser la concentration en dopants. Les implantations se sont déroulées à une température de 550 °C. L’optimisation des propriétés magnétiques et électroniques du SiC–Fe, de même que la compréhension des mécanismes physiques à l’origine du magnétisme induit, ont nécessité une caractérisation poussée de la microstructure des matériaux implantés. Les objectifs de ce travail ont été d’une part, de réaliser une étude à l’échelle atomique de la nanostructure en fonction des conditions d’implantations (température, fluence) et des traitements thermiques post-implantation, et d’autre part, de déterminer les propriétés magnétiques des matériaux implantés. Dans ce travail, nous avons montré par Sonde Atomique Tomographique, la présence de nanoparticules dont la taille moyenne augmente avec la température de recuit. La cartographie chimique des nanoparticules a permis de révéler l’existence de phases riches en Fe pour les échantillons recuits. L’étude magnétique (spectrométrie Mössbauer et Squid) a montré que la contribution ferromagnétique est due principalement aux nanoparticules magnétiques et/ ou aux atomes de fer magnétiques dilués dans la matrice. La corrélation entre les propriétés structurale et magnétique a permis de montrer que les atomes de fer dilués dans la matrice et substitués sur sites de silicium contribuent au signal ferromagnétique en dessous de 300 K. Nous avons donc montré dans ce travail, que la taille et la nature des phases présentes dans les nanoparticules dépendent des conditions d’implantation et des températures de recuit et qu’il est nécessaire de recuire les échantillons à haute température pour faire apparaître un ordre ferromagnétique<br>This PhD thesis focuses on the study of SiC, doped with Fe in order to elaborate a diluted magnetic semiconductor at room temperature for spintronic applications. The iron doping was carried out by ion implantation of multi-energy type (30-160 keV) at different fluences, leading to a 2% constant atomic concentration between 20 to 100 nm, followed by a high temperature annealing in the goal of homogenizing the dopant concentration. The implantation temperature during this process is 550 °C, in order to avoid amorphization. The optimization of the magnetic and electronic properties of SiC-Fe, as well as the understanding of the physical mechanisms at the origin of induced magnetism, require a thorough characterization of the microstructure of the implanted materials. The objectives of this work are, on the one hand, to carry out an atomic scale study of the nanostructure according to the implantation conditions (temperature, fluence) and the post-implantation annealing and the other hand, to characterize the magnetic properties of implanted materials. In this work, we have shown by atom probe tomographic, the existence of nanoparticles whose the average size increases with the annealing temperature. The chemical mapping of the nanoparticles shows the presence of the Fe-rich phases for the annealed samples. Magnetic study (Mössbauer spectrometry and Squid) shows the ferromagnetic contribution is due to the magnetic nanoparticles and/or the diluted Fe atoms in the matrix. The correlation between structural and magnetic properties allowed showing that diluted Fe atoms and substitute to Si sites contribute to the ferromagnetic contribution below 300 K. In coupling many characterization techniques in order to give a detailed description of the different studied samples, we have shown that the size and nature of the phase present in the nanoparticles depend on the implantation conditions and the annealing temperatures and consequently it is necessary to anneal our samples at high temperature to reveal ferromagnetic order
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Knechtel, Erik. "A compact atomic magnetometer for cubesats." Thesis, 2015. https://hdl.handle.net/2144/16303.
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By shining a precisely tuned laser through an atomic vapor, we can determine local mag-
netic field strength in scalar form and in a way that is not affected by temperature changes.
This technology has been used in space many times before on missions flown by NASA
and ESA, such as SWARM, Øersted, and CHAMP to calibrate accompanying vector mag-
netometers which are subject to offsets caused by temperature changes. The device we
constructed is a small, low-cost application of this scientific principle and opens up new
areas of scientific possibility for cubesats and the ability to define geomagnetic field struc-
tures on a small (<10km) scale as part of the ANDESITE cubesat mission being developed
at Boston University.
Previously, magnetic sensors in orbit have been flown individually on a single spacecraft
or in very small groups such as the International Sun-Earth Exporers (ISEE) and SWARM
which each used three separate spacecraft. This method of analyzing the geomagnetic field
cannot provide a spatial or time resolution smaller than that of the separation between
magnetic field readings. This project has focused on producing a tabletop demonstra-
tion of a compact sensor head which could enable measurements on unprecedented small
scales. Toward this end we have accomplished the construction and preliminary testing of
a compact sensor head which contains all necessary elements to function as a scalar atomic
magnetometer.
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Lin, Ying-Chen, and 林盈甄. "Shielded Potassium Atomic Magnetometer with Infrared Heating." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/47957337568813665500.
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碩士<br>國立臺灣大學<br>物理研究所<br>99<br>Theoretically, Alkali-metal magnetometers can be accurate as SQUID which is currently the most sensitive magnetic field sensors. We use high density Potassium atom vapor as our measurement sample, which is heated to 160±10℃, and is shielded by mu-metal for near zero magnetic field operation condition to reduce the noise from the spin exchange collision. The principle of the magnetometer is based on the resonant nonlinear magneto-optical effect that Larmor precession can be used to measure the spins of polarized atoms under the influence of the magnetic field.
In order to eliminate the overheating problem of the Helmholtz Coils and mu-metal caused by the hot-air heating method, we use an infrared light bulb as a thermal source and a quartz bar to transfer the heat to the Potassium cell. The temperature of the cell has been successfully raised up to 160±10℃ with no overheating problem and the system is more stable. Furthermore, a new method of finding zero magnetic fields is presented, in which the resonant signal with around 10μG width is observed. However, the signal drifts over time. To solve this problem, we have assumed some causes and target to solve them one by one.
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Hsu, Chia-Teng, and 許家騰. "Low Optical Noise Atomic Magnetometer with System Optimization." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/74151999807312230309.
Full textAbstract:
碩士<br>國立臺灣大學<br>應用物理所<br>100<br>High sensitivity magnetometers are applied in many fields including physics, biology, and geology. For detection of magnetic fields, low-temperature superconducting quantum interference device (SQUID) magnetometers give the most sensitive performance traditionally. However, to maintain SQUID working in the low temperature requires relatively high cost. Recently, alkali-metal magnetometers approach the same sensitivity level without this drawback. The principle of atomic magnetometers is based on the detection of Larmor spin precession in the magnetic fields. The fundamental sensitivity limit of atomic magnetometers comes from the shot noise which is associated with the transverse relaxation time. Spin exchanged collisions contributes to the transverse relaxation time mostly, and it can be reduced by operating in the environment with a near zero magnetic field. As the condition is introduced, it can reduce the noise limit down to 0.3 ft/√Hz. Such environment character is called spin exchange relaxation free (SERF). In this thesis, I analyze the system with simulations and experiments in an attempt to reach the optimization. The narrowest width 210 μG of the dispersion curves is read with the pump beam intensity 0.52 W/cm^2. Besides, the low optical noise system is built via applying a balance detector with appropriately adjusting the polarization of probe beam. The noise level decreases from mV to μV as compared from our previous system.
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Li, Chung-Lan, and 李鍾嵐. "Fabrication of Spin-Exchange-Relaxation-Free Atomic Magnetometer and Its Application." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/97939963469332895121.
Full textAbstract:
博士<br>國防大學理工學院<br>國防科學研究所<br>99<br>Recent developments in the technology of atomic magnetometers have enabled them to surpass SQUID (superconductive quantum interference devices) as the most sensitive devices for detecting and measuring magnetic fields. Their sensitivity is limited by the relaxation due to spin-exchange collisions. In this study, we design and build a Rb atomic magnetometer operating in the spin-exchange-relaxation-free (SERF) regime. We demonstrate a Rb magnetometer in which spin-exchange relaxation is completely eliminated by operating at high Rb density and low magnetic field. A Rb cell was put inside a 5-layer magnetic shield, and three current coils were used to eliminate the residual magnetic field in the shield. The Rb cell was filled with 2 atm of He and 60 Torr of N2 to reduce the collisions of Rb atoms with the glass wall in order to avoid relaxation. The cell was heated to 160 ℃ to produce a high density Rb vapor. Two tunable diode lasers operating near the Rb D1 line were used for the pump and probe beams. The detection sensitivity determined by signal-to-noise measurements with an applied ac magnetic field of known magnitude was about 8 pT/(Hz)1/2.
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Yang, Tsung-Lin. "Spin-Exchange Relaxation Free Potassium Atomic Magnetometer in the Un-Shielded Environment." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2807200821450300.
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