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Dissertations / Theses on the topic 'Spintronics'

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Published: 4 June 2021

Last updated: 15 June 2025

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Iurchuk, Vadym. "Spintronics under stress." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE024.

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Dans cette thèse, les interactions magnétoélectriques et optomagnétiques transmises par les contraintes dans les structures ferroélectriques/ferromagnétiques sont étudiées. Nous montrons que la dynamique des déformations du Pb(ZrxTi1-x)O3 aboutit à la manipulation électrique sous-coercitive de multi-états ferroélastiques rémanents. La mesure par une jauge résistive de ces états, ainsi que l'écriture et l'effacement électriques et le stockage ferroélastique, sont démontrés. La configuration des contraintes de matériaux ferroélectriques créée électriquement, permet de modifier l'anisotropie magnétique d'une couche ferromagnétique. Ce phénomène est utilisé pour contrôler le champ magnétique coercitif des composants magnétostrictifs des vannes de spin au moyen des déformations. L’irradiation lumineuse est également utilisée pour entraîner une photostriction rémanente dans le BiFeO3. Cette déformation rémanente est transférée à une couche ferromagnétique et permet un contrôle optique de la coercivité magnétique. Nous montrons comment les états magnétiques peuvent être écrits au moyen de la lumière et effacés par un champ électrique In this thesis, the strain-mediated magnetoelectric and optomagnetic interactions in ferroelectric/ferromagnetic structures are studied. The strain dynamics in Pb(ZrxTi1-x)O3 is shown to result in the sub-coercive electrical manipulation of its remanent ferroelastic multi-states. The resistive readout of these states provided by the strain gauge layers, together with the electrically-triggered ferroelastic writing, storage, and erasing, are demonstrated. These strain configurations created by electric fields in ferroelectrics can effectively impact the magnetic anisotropy of a ferromagnetic adlayer. This phenomenon is shown to control the magnetic coercive field of the magnetostrictive components of spin valves via the strain. Light irradiation is shown to result in remanent photostriction effect (photo-driven deformation) in BiFeO3. Such optically-induced remanent deformations can be transferred to a ferromagnetic adlayer and result in the optical control of the magnetic coercive force. It is shown here how magnetic states can be written by light and erased by an electric field

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Szumski, Douglas Stewart. "Single molecule spintronics." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535471.

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Slobodskyy, Taras. "Semimagnetic heterostructures for spintronics." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=983425892.

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Ulloa, Osorio Camilo Edgardo. "Aspects of antiferromagnetic spintronics." Tesis, Universidad de Chile, 2016. http://repositorio.uchile.cl/handle/2250/140609.

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Magíster en Ciencias, Mención Física La spintrónica se perfila como una de las corrientes mas atractivas y prometedoras dentro de la materia condensada gracias a la diversidad de fenómenos presentes, como el efecto Hall de spin, la magneto-resistencia gigante. En la spintrónica el estudio de materiales antiferromagnéticos es interesante pues dentro de sus propiedades se encuentran su abundancia natural y la posibilidad de disminuir las escalas temporal y espacial de los fenómenos presentes en ellos. Un ejemplo es la utilización de estos materiales en memorias magnéticas, pues gracias a la ausencia de magnetización neta en un material antiferromagnético es posible almacenar información en regiones de menor tamaño debido a la nula interacción dipolar entre dominios magnéticos. Esta tesis esté compuesta de tres trabajos teóricos orientados al desarrollo de la spintrónica antiferromagnética. En la primera parte se presenta la teoría efectiva de un sistema antiferromagnético no colineal. Para esto consideramos un sistema anisotrópico y con interacción de intercambio entre spines vecinos. A través de un parámetro de orden perteneciente al grupo de rotaciones estudiamos la dinámica de las excitaciones de baja energía del sistema obteniendo como resultado una familia de solitones topológicos que están descritos por la ecuación de sine-Gordon. Finalmente comparamos nuestros resultados con simulaciones numéricas de un sistema de momentos magnéticos obteniendo resultados completamente concordantes. La segunda parte corresponde al estudio de un cristal magnónico antiferromagnético. A partir de una teoría fenomenológica estudiamos la dinámica del campo de magnetización bajo el efecto de interacción de intercambio, y anisotropía uniaxial. A través de una modulación periódica de la anisotropía y del campo magnético caracterizamos el espectro de ondas de spín y las estructura de bandas del sistema. En la tercera y última parte se presenta el estudio de la generación de corrientes de spin mediante deformaciones de una red antiferromagnética gracias a efectos cuánticos. Este fenómeno, conocido como efecto piezospintrónico, es estudiado en dos modelos de interés: grafeno antiferromagnético y zinc-blende antiferromagnético. Este efecto, en conjunto con el efecto Hall de spín inverso pueden ser útiles para la detección de corrientes de spín puras. Spintronics is one of the most attractive and promising areas in condensed matter due to the diversity of phenomena present in it as the spin Hall e ect and the giant magnetoresistance. In spintronics the study of antiferromagnetic materials is interesting due to their natural abundance and the possibility of decreasing the temporal and spatial scale of the phenomena in which they are involved. One example of this is the use of antiferromagnetic materials in magnetic memories, where due to the absence of net magnetization it is possible to store information in smaller regions because of the null dipolar interaction between domains. This thesis is made of three theoretical works focused in di erent aspects of antiferromagnetic spintronics. In the rst chapter we present the e ective theory of a non collinear antiferromagnet. For this we consider an anisotropic system with exchange interaction among neighbor spins. By making use of an order parameter in the rotation group we study the dynamics of low energy excitations of the system obtaining as result a family of topological solitons which are described by the sine-Gordon equation. Finally we compare our results with numerical simulations of a system of magnetic moments obtaining totally concordant results. The second chapter corresponds to the study of an antiferromagnetic magnonic crystal. From a phenomenological theory we study the dynamics of the magnetization eld under the e ect of exchange interaction and uniaxial anisotropy. Through a periodic modulation of the anisotropy and of the magnetic eld we characterize the spin wave spectra and the band structure of the system. In the third and last chapter we show the study of generation of spin currents by deformation of an antiferromagnetic lattice thanks to quantum mechanical e ects. This phenomenon, known as piezospintronic e ect, is studied in two interesting models: antiferromagnetic graphene and antiferromagnetic zinc-blende. This e ect together with the inverse spin Hall e ect could be useful for the detection of pure spin currents. v Este trabajo ha sido parcialmente financiado por Proyecto Fondecyt N° 1150072, Proyecto Basal N° FB0807- CEDENNA, y Anillo de Ciencia y Tecnología N° ACT 1117

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Oyarzún, Medina Simón. "Spintronics in cluster-assembled nanostructures." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10166/document.

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Dans les dernières années, la miniaturisation progressive des dispositifs de stockage magnétique a rendu nécessaire de comprendre comment les propriétés physiques sont modifiées par rapport à l'état massif lorsque les dimensions sont réduites à l'échelle nanométrique. Pour cette raison, une méthode précise de préparation et caractérisation de nanostructures est extrêmement importante. Ce travail se concentre sur les propriétés magnétiques et de transport de nanoparticules de cobalt incorporées dans des matrices de cuivre. Notre dispositif expérimental nous permet de contrôler indépendamment la taille moyenne des agrégats, la concentration et la composition chimique. La production des agrégats de cobalt est basée sur la pulvérisation cathodique et l'agrégation dans la phase gazeuse. Cette source permet de produire des agrégats dans une large gamme de taille, de un à plusieurs milliers d'atomes. Dans un premier temps, nous avons étudié le rôle des interactions entre particules dans les propriétés de transport et magnétiques, en augmentant la concentration des nanoparticules de cobalt (à partir de 0.5 % à 2.5 % et 5 %). Nos résultats démontrent les précautions nécessaires et constituent une base solide pour de futures études sur les propriétés spintroniques des systèmes granulaires. Dans le but de décrire les propriétés magnétiques intrinsèques d'agrégats, nous avons préparé des échantillons fortement dilués (_0.5%) pour différents diamètres d'agrégats de 1.9 nm à 5.5 nm. Nous avons constaté que les propriétés magnétiques sont dépendantes de la taille. L'utilisation d'une caractérisation magnétique complète, sensible à la variation de l'anisotropie magnétique efficace, nous montre que l'anisotropie magnétique est dominée par les contributions de la surface ou de la forme des nanoparticules In the last years, the progressive miniaturization of magnetic storage devices has imposed the necessity to understand how the physical properties are modified with respect to the bulk when the dimensions are reduced at the nanometric scale. For this reason an accurate method of preparation and characterization of nanostructures is extremely important. This work focuses on the magnetic and transport properties of cluster-assembled nanostructures, namely cobalt nanoparticles embedded in copper matrices. Our setup allows us to independently control the mean cluster size, the concentration and the chemical composition. The cobalt cluster production is based on magnetron sputtering and gas phase aggregation. The performance of the source permits a wide range of cluster masses, from one to several thousand atoms. As a first step we studied the role of inter-particle interactions in the transport and magnetic properties, increasing the cobalt nanoparticle concentration (from 0.5% to 2.5% and 5%). Our results demonstrate the necessary precautions and constitute a solid basis for further studies of the spintronic properties of granular systems. Finally, in order to describe the intrinsic magnetic properties of cluster-assembled nanostructures, we prepared strongly diluted samples (_0.5%) for different cluster sizes from 1.9 nm to 5.5 nm. We found that the magnetic properties are size-dependent. Using a complete magnetic characterization, sensitive to the change in the effective magnetic anisotropy, we show that the magnetic anisotropy is dominated by the contributions of the surface or of the shape of the nanoparticles

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Oyarzún, Simón. "SPINTRONICS IN CLUSTER-ASSEMBLED NANOSTRUCTURES." Phd thesis, Université Claude Bernard - Lyon I, 2013. http://tel.archives-ouvertes.fr/tel-01019680.

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In the last years, the progressive miniaturization of magnetic storage devices has imposed the necessity to understand how the physical properties are modi- ed with respect to the bulk when the dimensions are reduced at the nanometric scale. For this reason an accurate method of preparation and characterization of nanostructures is extremely important. This work focuses on the magnetic and transport properties of cluster-assembled nanostructures, namely cobalt nanoparticles embedded in copper matrices. Our setup allows us to independently control the mean cluster size, the concentration and the chemical composition. The cobalt cluster production is based on magnetron sputtering and gas phase aggregation. The performance of the source permits a wide range of cluster masses, from one to several thousand atoms. As a rst step we studied the role of inter-particle interactions in the transport and magnetic properties, increasing the cobalt nanoparticle concentration (from 0.5% to 2.5% and 5%). Our results demonstrate the necessary precautions and constitute a solid basis for further studies of the spintronic properties of granular systems. Finally, in order to describe the intrinsic magnetic properties of cluster-assembled nanostructures, we prepared strongly diluted samples (<0.5%) for di erent cluster sizes from 1.9 nm to 5.5 nm. We found that the magnetic properties are size-dependent. Using a complete magnetic characterization, sensitive to the change in the e ective magnetic anisotropy, we show that the magnetic anisotropy is dominated by the contributions of the surface or of the shape of the nanoparticles.

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Sambricio, Garcia Jose Luis. "Graphene-hybrid devices for spintronics." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/graphenehybrid-devices-for-spintronics(e552a341-6af9-45fb-ba16-d9c43c3412c8).html.

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This thesis explores the use of 2D materials (graphene and hBN) for spintronics. Interest on these materials in spintronics arose from theoretical predictions of high spin filtering in out-of-plane transport through graphene and hBN sandwiched by ferromagnets. Similarly, 5-layer graphene was forecast to be a perfect spin filter. In the case of in-plane spin transport, graphene was expected to be an excellent material due to its low spin-orbit coupling and low number of defects. Although there already exist experimental works that attempted to explore the aforementioned predictions, they have failed so far to comply with the expected results. Earlier experimental works in graphene and hBN out-of-plane spin transport achieved low spin filtering on the order of a few percent; while spin relaxation parameters in graphene for in-plane spin transport remained one or two orders of magnitude below the predicted values. In the case of vertical devices, the failure to meet the theoretical expectations was attributed to the oxidation of the ferromagnets and the lack of an epitaxial interface between the later and the graphene or hBN. Similarly, the exact mechanisms that lead to high spin relaxation for in-plane spin transport in graphene are not completely understood, in part due to the low-quality of the explored devices. In this thesis we analyze new architectures and procedures that allowed us to fabricate ultraclean and oxidation-free interfaces between ferromagnets and graphene or hBN. In these devices we encountered negative and reversible magnetoresistance, that could not be explained with the previous theoretical models. We propose a new model based on a thorough characterization of the devices and well-known properties of graphene that were not taken into account in the previous model. We also employed a novel type of contact to graphene (1D-contacts) and applied it for the first time to achieve spin-injection in graphene. The main advantage of this type of contact is the full encapsulation of graphene with hBN, which leads to high quality graphene spintronic devices.

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Li, Yang. "Single Molecule Spintronics and Friction." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou151561792063398.

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Kiziroglou, Michail E. "Integration of spintronics into silicon microelectronics." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435718.

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Laloë, Jean-Baptiste. "Atomic-scale interface magnetism for spintronics." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613160.

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Bataiev, Yurri N. "Ferromagnetic Resonance Study of Spintronics Materials." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236192587.

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Kelley, Christopher Stephen. "Spatially resolved infrared spectroscopy for spintronics." Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/6589/.

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Magnetoresistance, a change in the resistance of a material in an externally applied magnetic field, is an extremely important property of magnetic materials. The discovery of giant magnetoresistance has led to a revolution in computing, driving increases in storage density of hard disks and paving the way for commerical spintronic devices. Conventionally, magnetoresistance is measured by sourcing a current through a material and measuring the voltage. Ohm’s law is used to calculate the resistance of the material with and without an external magnetic field, the difference between these results being the magnetoresistance. This technique is limited as it does not offer spatial resolution, so variations in magnetoresistance in a material can not be detected. Electrical contact must also be made to the material, which can cause damage to the material being measured. The magnetorefractive effect, the change in the reflection spectrum of a material in an external magnetic field, can be used as an alternative to the electrical measurement of magnetoresistance. The magnetorefractive effect allows non-contact measurements of magnetoresistance to be made, so the material remains undamaged, whilst also offering the possibility of spatial resolution. Modelling the spectral magnetorefractive effect can also aid in understanding the underlying physical mechanism behind the magnetoresistance, which is impossible with an electrical measurement. Infrared reflection microspectroscopy was used to observe variations in reflectivity across Fe3O4 thin films. By modelling these variations, it was possible to estimate the chemical composition of the samples as well as observe any variations in composition across them. A spatial variation in magnetoresistance was observed across a CoFe/Cu multilayer using the magnetorefractive effect, whilst also obtaining the spectral resolution necessary to model the system, the first time such a measurement has been performed. The correlation between the magnetorefractive effect and magnetoresistance had been predicted to be strong in the far-infrared by previous theoretical work. The magnetorefractive effect in the far-infrared was measured for a series of spin valves, demonstrating this strong correlation in the far-infrared for the first time, providing long awaited experimental confirmation of this theoretical prediction.

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Loreto, Renan Pires. "Topological states applied to spintronics devices." Universidade Federal de Viçosa, 2018. http://www.locus.ufv.br/handle/123456789/20365.

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Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2018-06-28T18:08:29Z No. of bitstreams: 1 texto completo.pdf: 9737599 bytes, checksum: fd1c96dcfb7c14f5fa206a440c3c5095 (MD5) Made available in DSpace on 2018-06-28T18:08:29Z (GMT). No. of bitstreams: 1 texto completo.pdf: 9737599 bytes, checksum: fd1c96dcfb7c14f5fa206a440c3c5095 (MD5) Previous issue date: 2018-04-24 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Neste trabalho estudamos tres importantes sistemas magnéticos extensamente pesquisados nas últimas décadas. Na primeira parte, a proposta recente da utilização de skyrmions magnéticos, que são excitações topológicas tipo quasi-partícula em ferromagnetos, em memórias tipo racetrack, tem atraído a atenção de pesquisadores nos últimos anos abrindo um novo campo de estudo chamado skyrmionics, que é uma tentativa de utilizar estas estruuras magnéticas como transportadores de informação na próxima geração de de dispositivos spintrônicos. Para a utilização de skyrmions magnéticos, em alguns sistemas é necessário a inclusão de interação Dzyaloshinskii-Moriya e campos magnéticos externos no sistema. Neste trabalho, nós exploramos um sistema sem estes requisitos. Primeiro, propusemos um modo controlado de criação de skyrmions e skyrmioniums impressos em em uma nanofita de material ferromagnético com magnetização fora do plano. Após isso, investigamos o destacamento da estrutura da região abaixo de um nanodisco, responsável por imprimir esta estrutura. O transporte é feito por spin transfer torque devido a pulsos de corrente elétrica spin polarizada aplicadas na nanofita. A detecção da estrutura é feita por magnetoresistência túnel. Esta estrutura que se move, após deixar a região abaixo do disco, não é mais considerada um skyrmion e, calculando como a carga topológica evolui, a estrutura foi chamada de sóliton magnético ressonante. A segunda parte cobre os efeitos de geração de correntes puras de spin por Spin Pumping e efeito Seebeck de Spin e a conversão dessas correntes de spin em correntes de carga em isolantes topológicos a temperatura ambiente. A conversão de corrente de spin em corrente de carga é devido ao efeito Edelstein Inverso (IEE) que é possivel devido ao ’spin-momentum locking’ do elétron no nível de Fermi devido ao campo de Rashba. As medidas nas duas técnicas levaram ao mesmo valor do parâmetro IEE, mostrando que ambos os resultados são maneiras eficientes de converão de corrente de spin em corrente de carga. Na terceira parte, redes de nanomagnetos projetados para assemelhar-se a gelos de spin (estados magnéticos desordenados) e são conhecidos como gelos de spin artificiais e, estudos teóricos e experimentais da termodinâmica nestas redes. Nas redes retangulares de gelos de spin artificiais espera-se que mostrem diferentes transições de fase mudando a geometria do sistema. Esta dinâmica gerada por efeitos geométricos abrem uma possibilidade de explorar diferentes estados fundamentais e geração de monopolos magnéti- cos por efeitos térmicos. Aqui, mostramos que uma rede particular de gelos de spin artificiais se mostram com menos restrições para que as nanoilhas mudem magnetização em uma rede em particular e, comparndo o impacto de efeitos térmicos em mudanças de magnetização em diferentes sistemas, é possível encontrar o fenÃt’meno chamado geometrotermodinâmica. In this work we study three important magnetic systems extensively researched in the past decades. In the first part, the recent proposition of the use of magnetic skyrmions, which are topological particle-like excitations in ferromagnets, in racetrack memories, have attracted a lot of attention recently opening up a new field of study called skyrmionics which is an attempt to use those magnetic structures as information carriers in next generation of spintronic devices. For usage of magnetic skyrmions, in some systems is necessary to include the Dzyaloshinskii- Moriya interaction (DMI) and the out-of-plane magnetic field into the system. In this work, we explore a system without these requirements. First, we propose a controlled way for the creation of magnetic skyrmions and skyrmioniums imprinted in a perpendicular magnetized ferromagnetic nanotrack. Then we investigate the detachment of the imprinted spin textures from the underneath of the nanodisk, the transport by the spin-transfer torque imposed by spin-polarized current pulses applied in the nanotrack and the detection by Tunnel Magnetoresistance (TMR). We notice that the moving structure is not a skyrmion after is detached, and by calculating how the topological charge behaves, we have called it the resonant magnetic soliton (RMS). The second part covers the generation of spin currents by Spin Pumping and Spin Seebeck effects and the conversion of this spin current to charge current in (Bi 0.22 Sb 0.78 ) 2 T e 3 topological insulators at room temperature. The spin-to-charge current conversion is attributed to the inverse Edelstein effect (IEE) made possible by the spin-momentum locking in the electron Fermi contours due to the Rashba field. The measurements by the two techniques yield the same value for the IEE parameter, showing that those methods can be an efficient way to the spin to charge current in topological insulators. In the third part, arrays of nanomagnets designed to resemble spin ice materials (disordered magnetic states) are known as artificial spin ices (ASI). Here we study, both theoretically and experimentally the thermodynamic effects on streched arrays of spin ices. The rectangular artificial spin ices (RASI) is expected do show different phase transitions by changing the geometry of the system. This geometrically driven dynamics in ASI can open up the panorama of exploring distinct ground states and thermally generated magnetic monopole excitations. Here, it is shown that a particular RASI lattice experience less restriction to flip precisely in a kind of rhombic lattice and by comparing the impact of thermal effects on the spin flips in these three appropriate different RASI arrays, it is possible to find the phenomenon that we call ASI geometrothermodynamics.

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Verduci, Tindara. "Optimizing OFETs properties for spintronics applications." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE025/document.

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Cette thèse a pour but d’étudier le transport de porteur de charge au sein de polymères conjugués, avec comme finalité d’identifier les propriétés des appareils d’électronique organique appropriées pour des applications dans la spintronique organique. Nous avons analysé des échantillons planaires, de géométries latérales, qui offrent la possibilité d’étudier les propriétés de transport sous l’application de différents stimulus et la détection le transport de longue distance du moment angulaire (spin), au sein de semi-conducteurs organiques (OSC). Dans cette configuration, des critères bien établis doivent être satisfait pour réaliser le transport diffusif d’un courant de spin polarisé au travers d’un matériel organique. Nous avons analysé ces diffèrent critères et trouvé des matériaux dont les propriétés physiques fournissent une solution satisfaisante. Le résultat de ce travail fut la création de transistors à effet de champ organiques dont les propriétés répondent au besoin des applications de spintronique In this thesis, charge carrier transport in conjugated polymers is studied with the aim to identify organic electronics devices properties suitable for applications in organic spintronics. We investigate planar samples, in a lateral geometry, which offer the possibility to study transport properties under the application of different stimuli and to detect long-range spin transport in OSCs. In this configuration, well-established criteria must be satisfied to realize diffusive-like transport of a spin-polarized current through an organic material. We analyse these criteria and find possible materials properties solutions. The outcome is the realization of organic field-effect transistors with properties ad hoc for spintronics applications

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Fache, Thibaud. "Iridium-based synthetic ferrimagnets for spintronics." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0011.

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Les matériaux ferrimagnétiques de synthèse à aimantation perpendiculaire ont été étudiés extensivement lors de la dernière décennie. Leurs propriétés d’électronique de spin, notamment en ce qui concerne les propagations de parois magnétiques par l’injection d’un courant, en font des candidats idéaux pour les applications de mémoires magnétiques de type racetrack. Du fait de propriétés remarquables concernant d’une part la génération et le transport de courant de spin par couple de spin orbite, et d’autre part le couplage d’échange de type RKKY, l’iridium est un excellent candidat en tant que matériau de spacer pour les matériaux ferrimagnétiques de synthèse. Dans ce manuscrit, nous étudions des multicouches ferrimagnétiques de synthèse composées de deux couches de cobalt séparées par un spacer d’iridium. Nous présentons d’une part l’optimisation de la croissance de tels matériaux, de sorte à obtenir un système modèle en vue d’applications pour des « racetrack memories ». Nous maximisons ainsi le couplage d’échange antiferromagnétique entre les couches de cobalt et l’aimantation à rémanence. D’autre part, nous étudions les propriétés de transport de spin de l’iridium grâce à des méthodes de résonance magnétique par pompage en spin. Nous en concluons que les matériaux ferrimagnétiques de synthèse à base d’iridium sont des systèmes modèles pour la fabrication de « racetrack memories » Synthetic ferrimagnets with perpendicular magnetic anisotropy have been studied extensively in the past decades. Their outstanding properties in terms of spintronics, especially concerning the current-induced magnetic domain wall propagation lead us to contemplate them as promising candidates as materials for magnetic racetrack memories. Besides, considering the remarkable properties of iridium concerning the transport and the generation of pure spin currents by means of spin orbit torque, as well as its large RKKY coupling properties, this material seems to be an excellent material as a spacer for synthetic ferrimagnets. In this manuscript, we study magnetic multilayers composed of two magnetic layers of cobalt separated by an iridium spacer. We optimise the growth of these multilayers by choosing the most adequate thicknesses, so as to obtain a model system for racetrack memories applications. Thus, we maximise the antiferromagnetic exchange between the cobalt layers, and the remanence magnetisation. Besides, we study the spin current generation and transport properties of iridium by spin pumping ferromagnetic resonance means. We draw the conclusion that iridium-based synthetic ferrimagnets can be considered as model systems for racetrack memory technology

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Kameš, Jaroslav. "Studium magnetických nanostruktur pro spintroniku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228666.

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The Cu/NiFe/Cu/Co/(CoOx) spin-valves have been prepared by the ion-beam sputtering method. Their GMR ratio and the time stability have been investigated by the magnetoresistance and the MOKE measurements at room temperature. The reproducibility of the preparation of the samples have been studied as well, i.e. two identically configurations of the layers should have the same magnetotransport properties.

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Al, Daboochah Hashim Mohammed Jabbar. "Ferromagnet [and] phthalocyanines heterostructures for spintronics applications." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE040.

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La mise en évidence d’effets de polarisation d’échange (“exchange bias”, EB) ouvre de nouvelles perspectives dans le domaine émergeant de la spintronique organique. Dans une première partie de la thèse, on étudie l’EB des systèmes Co/MPc et Py/MPc (M=Mn, Co, Fe, Zn) par magnétométrie. Pour tous ces systèmes, l’EB est observé avec des températures de blocage de 100K environ. Ces études sont complétées par des mesures de résonance ferromagnétique confirmant les valeurs du champ de polarisation. Dans une troisième partie, on étudie les propriétés magnétiques des tricouches Co/Pc/Co. Les cycles d’hystérèse présentent des marches indiquant un renversement séquentiel des couches de cobalt. A basse température, on observe de l’anisotropie unidirectionnelle pour les deux couches mais leurs champs de polarisation diffèrent Observation of exchange bias (EB) phenomenon by using molecular materials as a pinninglayer open the horizon for tremendous perspective in the field of organic spintronics. Thefirst part of the thesis is devoted to the study of EB of Co/MPc and Py/MPc (M=Mn, Co, Fe,Zn) by static magnetometry. The existence of EB is evidenced in all Pc molecules with block-ing temperature around 100K. The second part is devoted to the study of EB by dynamicFMR measurements. The values of EB measured by this method are compatible with staticmagnetometry measurements. The third part is devoted to study magnetic properties of thetrilayer Co/Pc/Co systems. Hysteresis loops exhibit a stepped shape indicative of successivereversal of each layer. Low temperature loops show that both Co layers experience unidi-rectional anisotropy after field cooling, with differing bias fields

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Tyagi, Pawan. "FABRICATION AND CHARACTERIZATION OF MOLECULAR SPINTRONICS DEVICES." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/614.

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Fabrication of molecular spin devices with ferromagnetic electrodes coupled with a high spin molecule is an important challenge. This doctoral study concentrated on realizing a novel molecular spin device by the bridging of magnetic molecules between two ferromagnetic metal layers of a ferromagnetic-insulator-ferromagnetic tunnel junction on its exposed pattern edges. At the exposed sides, distance between the two metal electrodes is equal to the insulator film thickness; insulator film thickness can be precisely controlled to match the length of a target molecule. Photolithography and thin-film deposition were utilized to produce a series of tunnel junctions based on molecular electrodes of multilayer edge molecular electrodes (MEME) for the first time. In order to make a microscopic tunnel junction with low leakage current to observe the effect of ~10,000 molecules bridged on the exposed edge of a MEME tunnel barrier, growth conditions were optimized; stability of a ~2nm alumina insulator depended on its ability to withstand process-induced mechanical stresses. The conduction mechanism was primarily 1) tunneling from metal electrode to oranometalic core by tunneling through alkane tether that acts as a tunnel barrier 2) rapid electron transfer within the oranometalic Ni-CN-Fe cube and 3) tunneling through alkane tether to the other electrode. Well defined spin-states in the oranometalic Ni-CN-Fe cube would determine electron spin-conduction and possibly provide a mechanism for coupling. MEME with Co/NiFe/AlOx/NiFe configurations exhibited dramatic changes in the transport and magnetic properties after the bridging of oranometalic molecular clusters with S=6 spin state. The molecular cluster produced a strong antiferromagnetic coupling between two ferromagnetic electrodes to the extent, with a lower bound of 20 erg/cm,2 that properties of individual magnetic layers changed significantly at RT. Magnetization, ferromagnetic resonance and magnetic force microscopy studies were performed. Transport studies of this configuration of MEME exhibited molecule-induced current suppression by ~6 orders by blocking both molecular channels and tunneling between metal leads in the planar 25μm2 tunnel junction area. A variety of control experiments were performed to validate the current suppression observation, especially critical due to observed corrosion in electrochemical functionalization step. The spin devices were found to be sensitive to light radiation, temperature and magnetic fields. Along with the study of molecular spin devices, several interesting ideas such as ~9% energy efficient ultrathin TaOx based photocell, simplified version of MEME fabrication, and chemical switching were realized. This doctoral study heralds a novel molecular spin device fabrication scheme; these molecular electrodes allow the reliable study of molecular components in molecular transport.

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Foronda, Jamie. "Germanium as a platform for semiconductor spintronics." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/91299/.

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The field of semiconductor spintronics is relatively underdeveloped when compared to its metallic counterpart which has found great success in the computer storage industry in hard disk drive head technology and to a lesser extent non-volatile and robust (M)RAM. The use of semiconductors in spintronics is promising with the ability to modulate spins via a gate controlled spin-orbit interaction allowing for spintronic logic and computation devices. Combining this with dilute ferromagnetic semiconductors, which have been suggested as a base for semiconductor MRAM, it may even be possible to integrate MRAM and logic into a single chip to allow for further miniaturisation of devices. In this thesis we look into the suitability of Ge as a platform for semiconductor spintronics verses other popular alternatives such as Si and GaAs. The first section of this thesis looks at evidence of a strong spin-orbit interaction in low temperature magnetoresistance curves measured in a high mobility (777,000 cm2V-1s-1) Ge 2DHG. Despite the lack of beatings in Subnikov de Haas oscillations, which often serves as an indicator of a strong spin-orbit coupling, weak antilocalisation like behaviour is seen at low fields. The spin splitting energy extracted from the weak antilocalisation and found to be 0.8meV with a Rashba parameter of 3.2x10-28 eVm3. The spin split energy is comparable to other Ge and III-V 2DHGs, however the Rashba parameter is in fact higher, which we believe is attributed to the high level of remote doping. The second section focuses on the treatment of ferromagnet/oxide spin tunnel contacts on Ge deposited by evaporation or sputtering, both of which are common in industrial scale fabrication. Annealing XPS studies are conducted on these contacts to examine the temperature limits at which annealing treatments can be done before contacts degrade. Transition line measurements are also examined to look at the electrical characteristics of the deposited contacts. The final section focuses on the fabrication and measurements of Hanle devices on n-Ge. The extracted spin lifetimes are of the same order as those measured in similarly doped Ge devices, however strong temperature dependencies of both the spin lifetime and spin accumulation signal suggest that the signal measured is strongly influenced by local states within the oxide barrier.

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Torresani, Patrick. "Hole quantum spintronics in strained germanium heterostructures." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY040/document.

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Le travail exposé dans cette thèse de doctorat présente des expériences à basse température dans le domaine de la spintronique quantique sur des hétérostructures à base de germanium. Tout d’abord, les avantages attendus du germaniumpour la spintronique quantique sont exposés, en particulier la faible interaction hyperfine et le fort couplage spin-orbite théoriquement prédits dans le Ge. Dans un second chapitre, la théorie des boites quantiques et systèmes à double boite sont détaillés, en se focalisant sur les concepts nécessaires à la compréhension des expériences décrites plus tard, c’est-à-dire les effets de charge dans les boites quantiques et double boites, ainsi que le blocage de spin de Pauli. Le troisième chapitre s’intéresse à l’interaction spin-orbite. Son origine ainsi que ses effets sur les diagrammes d’énergie de bande sont discutés. Ce chapitre se concentre ensuite sur les conséquences de l’interaction spin-orbite spécifiques aux gaz bidimensionnels de trous dans des hétérostructures de germanium, c’est-à-dire l’interaction spin-orbite Rashba, le mécanisme de relaxation de spin D’Yakonov-Perel ainsi que l’antilocalisation faible.Le chapitre quatre présente des mesures effectuées sur des nanofils coeur coquillede Ge/Si. Dans ces nanofils une boite quantique se forme naturellement et celui-ci est étudié. Un système à double boite quantiques est ensuite formé par utilisation de grilles électrostatiques, révélant ainsi du blocage de spin de Pauli.Dans le cinquième chapitre sont détaillés des mesures demagneto-conductance de gas de trous bidimensionnels dans des hétérostructures de Ge/SiGe contraints dont le puit quantique se situe à la surface. Ces mesuresmontrent de l’antilocalisation faible. Les temps de transport caractéristiques sont extraits ainsi que l’énergie de séparation des trous 2D par ajustement de courbe de la correction à la conductivité due à l’antilocalisation. De plus, les mesures montrent une suppression de l’antilocalisation par un champ magnétique parallèle au puit quantique. Cet effet est attribué à la rugosité de surface ainsi qu’à l’occupation virtuelle de sous-bandes inoccupées.Finalement, le chapitre six présente des mesures de quantisation de la conductancedans des hétérostructures de Ge/SiGe contraints dont le puit quantique est enterré. Tout d’abord, l’hétérostructure est caractérisée grâce à des mesures de magneto-conductance dans une barre de Hall. Ensuite, un second échantillon dessiné spécialement pour la réalisation de points de contact quantiques est mesuré. Celui-ci montre des marches de conductance. La dépendance en champ magnétique de ces marches est mesurée, permettant ainsi une extraction du facteur gyromagnétique de trous lourds dans du germanium This thesis focuses on low temperature experiments in germaniumbased heterostructure in the scope of quantumspintronic. First, theoretical advantages of Ge for quantum spintronic are detailed, specifically the low hyperfine interaction and strong spin orbit coupling expected in Ge. In a second chapter, the theory behind quantum dots and double dots systems is explained, focusing on the aspects necessary to understand the experiments described thereafter, that is to say charging effects in quantum dots and double dots and Pauli spin blockade. The third chapter focuses on spin orbit interaction. Its origin and its effect on energy band diagrams are detailed. This chapter then focuses on consequences of the spin orbit interaction specific to two dimensional germaniumheterostructure, that is to say Rashba spin orbit interaction, D’Yakonov Perel spin relaxation mechanism and weak antilocalization.In the fourth chapter are depicted experiments in Ge/Si core shell nanowires. In these nanowire, a quantumdot formnaturally due to contact Schottky barriers and is studied. By the use of electrostatic gates, a double dot system is formed and Pauli spin blockade is revealed.The fifth chapter reports magneto-transport measurements of a two-dimensional holegas in a strained Ge/SiGe heterostructure with the quantum well laying at the surface, revealing weak antilocalization. By fitting quantumcorrection to magneto-conductivity characteristic transport times and spin splitting energy of 2D holes are extracted. Additionally, suppression of weak antilocalization by amagnetic field parallel to the quantum well is reported and this effect is attributed to surface roughness and virtual occupation of unoccupied subbands.Finally, chapter number six reportsmeasurements of quantization of conductance in strained Ge/SiGe heterostructure with a buried quantumwell. First the heterostructure is characterized by means ofmagneto-conductance measurements in a Hall bar device. Then another device engineered specifically as a quantum point contact is measured and displays steps of conductance. Magnetic field dependance of these steps is measured and an estimation of the g-factor for heavy holes in germanium is extracted

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DiLullo, Andrew R. "Manipulative Scanning Tunneling Microscopy and Molecular Spintronics." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1363821351.

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Zhaksylykova, Indira. "Magneto-optic detection limits for semiconductor spintronics." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX099/document.

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Ce travail explore l'utilisation de l'effet magnéto-optique pour étudier la dynamique de spin des électrons de conduction dans les semi-conducteurs non magnétiques lorsqu'ils sont pompés avec des photons polarisés circulairement. En général, les moments magnétiques hors-équilibre induits optiquement dans les semi-conducteurs non magnétiques sont plus petits que ceux des matériaux magnétiques. L'effet magnéto-optique en principe offre une sensibilité suffisante pour détecter ces faibles moments magnétiques via une mesure de rotation Faraday dans la limite de bruit de photons. Nous avons comparés trois méthodes de détection: les polariseurs partiellement croisés, l’interféromètre de Sagnac et le pont optique. L'interféromètre de Sagnac se révèle fonctionnellement équivalent aux polariseurs partiellement croisés, avec une sensibilité diminuée par la perte de photons à chacun des séparateurs de faisceaux nécessairement présents dans cette configuration expérimentale. Par contre, il a été démontré précédemment que les interféromètres de Sagnac permettent de faire la distinction entre les rotations dites réciproques et non réciproques, et cette thèse propose de nouvelles géométries de Sagnac pour distinguer les rotations en fonction de leurs symétries en temps et en parité. La technique du pont optique présente les meilleures performances. Elle permet une mesure de l'angle de rotation de Faraday limitée par le bruit de photons, même avec des puissances lumineuses importantes reçues par les détecteurs, ce qui permet d'obtenir la meilleure figure de mérite possible. Dans les expériences conduites sur des matériaux magnétiques, un bruit de quelques nrad/√Hz a été mesuré pour une puissance de sonde de 10 mW. Une série de mesures de rotation Faraday pompe-sonde à température ambiante a été réalisée sur GaAs pompé optiquement. Les plus grands signaux sont obtenus lorsque le moment magnétique généré et détecté est maximisé en focalisant fortement les faisceaux pompe et sonde et en choisissant une longueur d'onde de la sonde accordée à une résonance optique dans la structure électronique. Les mesures en champ magnétique transversal montrent un champ Hanle de 0.43 T, à partir duquel on déduit la durée de vie de spin de 88 ps This work explores the use of the magneto-optical Kerr effect to study conduction electron spin dynamics in non-magnetic semiconductors when pumped with circularly polarized photons. Typically, non-equilibrium, optically-induced magnetic moments in non-magnetic semiconductors are orders of magnitude smaller than those of magnetized materials, including both magnetic and non-magnetic materials in an external magnetic field. The magneto-optical Kerr effect in principal offers sufficient sensitivity to detect such small magnetic moment via a measurement of the Faraday rotation angle of a probe beam in the photon shot noise limit. Three detection configurations have been experimentally compared: partially crossed polarizers, a Sagnac interferometer and an optical bridge. The Sagnac interferometer is shown to be functionally equivalent to partially crossed polarizers, although its sensitivity is compromised by lost photons at each of the obligatory beam splitters present in such a geometry. On the other hand, it has previously been shown that Sagnac interferometers can distinguish between so-called reciprocal and non-reciprocal rotations, and this thesis proposes novel Sagnac geometries to distinguish rotations according to their time and parity symmetries. The optical bridge technique allows for a photon-shot noise limited measurement of the Faraday rotation angle, even with large photon intensities on the detectors, thereby yielding the best possible figure-of-merit. In demonstrations on magnetic materials, a noise floor of a few nrad//√Hz was measured for a probe power of 10 mW. A series of room-temperature, pump-probe Faraday rotation measurements is performed on optically pumped GaAs to compare and contrast this method with standard polarized photo-luminescence techniques. The largest signals are found when the locally probed moment is maximized by strongly focusing the pump and probe beams, and by choosing a probe wavelength tuned to an optical resonance in the electronic structure. Measurements in transverse magnetic field show a Hanle field of 0.43 T, from which the spin lifetime of 88 ps is deduced

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Guillemard, Charles. "Half-metal magnets Heusler compounds for spintronics." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0110.

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L'amélioration des techniques de dépôts et l’évolution de la compréhension de la physique de la matière condensée a conduit à la découverte de phénomènes nouveaux en électronique de spin (spintronique). En particulier, le retournement de l’aimantation par couple de transfert de spin et couple spin-orbite, ainsi que le développement de dispositifs basés sur la propagation d’ondes de spin ont fait de l’amortissement magnétique de Gilbert un paramètre central pour les futures technologies de stockage et de traitement de l’information. Dans cette étude, la prédiction de valeurs très faibles d’amortissement dans les alliages d’Heusler demi métaux magnétiques Co2MnZ est expérimentalement observée et directement corrélée à la structure électronique sous-jacente. En effet, en substituant l’élément Z dans des couches minces monocristallines de haute qualité de Co2MnZ (Z= Al, Si, Ga, Ge, Sn, Sb) faites par épitaxie par jet moléculaire, les propriétés électroniques telles que le gap de spin minoritaire, la position du niveau de Fermi et la polarisation en spin peuvent être accordées et leurs conséquences sur la dynamique de l’aimantation sont analysées. Les résultats expérimentaux nous permettent de comprendre la relation existante entre la structure électronique mesurée et la valeur d’amortissement magnétique, ainsi que de les comparer aux calculs ab initio. Les valeurs d’amortissement entre 4.1 x10-4 et 9 x10-4 pour Co2MnSi, Co2MnGe, Co2MnSn et Co2MnSb sont les plus petites valeurs jamais reportées pour des couches conductrices et constituent une preuve expérimentale qui confirme les prédictions théoriques sur ces alliages d’Heusler demi métaux magnétiques. Ensuite, la relation entre l’amortissement magnétique de Gilbert et le temps de désaimantation ultra-rapide induit par pulse laser dans la série d’alliages quaternaires Co2MnSixAl1-x à polarisation en spin variable est étudiée. Cette partie vise à vérifier des modèles théoriques qui essaient d’unifier ces deux quantités vivant sur des échelles de temps différentes. Finalement, les propriétés structurales et magnétiques de super réseaux Mn3Ga/Co2YZ sont étudiées dans le but de combiner un amortissement de Gilbert très faible, un gap de spin minoritaire ainsi que l’aimantation perpendiculaire aux plans des couches, une caractéristique indispensable pour des dispositifs à faible consommation d’énergie Improvements in thin film elaboration methods and a deeper understanding of condensed matter physics have led to new exciting phenomena in spin electronics (spintronics). In particular, magnetization reversal by spin-orbit and spin-transfer torque as well as the development of spin waves based devices have placed the Gilbert magnetic damping coefficient as a key parameter for future data storage and information processing technologies. The prediction of ultralow magnetic damping in Co2MnZ Heusler half-metal magnets is explored in this study and the damping response is shown to be linked to the underlying electronic structure. By substitution of the Z element in high quality Co2MnZ (Z=Al, Si, Ga, Ge, Sn and Sb) epitaxial thin films grown by molecular beam epitaxy, electronic properties such as the minority-spin band gap, Fermi energy position in the band gap, and spin polarization can be tuned and the consequences for magnetization dynamics analyzed. Experimental results allow us to directly explore the interplay of spin polarization, spin gap and Fermi energy position, with the magnetic damping obtained in these films (together with predictions from ab initio calculations). The ultralow magnetic damping coefficients measured in the range from 4.1 x10-4 to 9 x10-4 for Co2MnSi, Co2MnGe, Co2MnSn and Co2MnSb are the lowest values ever reported in conductive layers and offer a clear experimental demonstration of theoretical predictions on half metal magnetic Heusler compounds. Then, the relation between the Gilbert damping and the ultrafast demagnetization time in quaternary Co2MnSixAl1-x compounds with a tunable spin polarization is analyzed. This way, it is possible to confront theoretical models unifying those two quantities that live in different timescales. Finally, structural and magnetic properties of Mn3Ga/Co2YZ Heusler superlattices are investigated in order to combine ultralow Gilbert damping coefficient, minority spin band gap and perpendicularly magnetized heterostructures, another requirement for low energy consumption devices. Through the present work, we aim to prove that Heusler compounds provide an excellent playground to study fundamental magnetism and offer a pathway for future materials design

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Guillemard, Charles. "Half-metal magnets Heusler compounds for spintronics." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0110.

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Franco, Pujante Carlos. "Organic free radicals for molecular electronics and spintronics." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399515.

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La presente tesis doctoral se centra en el campo de la electrónica molecular, en particular se ocupa del desarrollo de nuevos dispositivos moleculares y del estudio de los fenómenos de transferencias electrónica asociados a ellos. Las propiedad de los policloro trifenilmetil radicales (PTM) han sido utilizadas en este trabajo para investigar los diferentes mecanismos de transferencia de carga asociados a varios sistemas en los cuales los PTM están involucrados. En la primera parte de la tesis se ha descrito el estudio de los procesos de transferencia de carga a través de dos diferentes familias de hilos moleculares, una de vinilo tiofene y la otra de oligo-p-fenilenos vinilenos fusionado conectados a dos moléculas de PTM las cuales actúan como dadores y aceptores de electrones en sistemas de valencia mixta D-B-A. Estos sistemas han sido completamente caracterizados por diferentes técnicas espectroscópicas en sus diferentes estados de oxidación: neutro, de valencia mixta y oxidada. Además, los mecanismos para la transferencia electrónica intermolecular a través de estos hilos moleculares han sido elucidados. En la segunda parte de la tesis ha sido reportada la síntesis de una familia de derivados de PTM con grupos tiol conectados al PTM a través de un cadena alquílica de diferentes longitudes, capaces de formar monocapas auotensambladas (SAM) sobre substratos de oro. Asimismo, se ha estudiado los mecanismos de transferencia electrónica a través de las SAMs de PTM en sus diferentes estados de oxidación, contactadas estas por el electrodo de eutéctico galio-indio y por el microscopio de efecto túnel. Para finalizar, en la última parte de la tesis, se ha reportado el estudio de las propiedades magnéticas y eléctricas de dos derivados de PTM en break-juction unimoleculares de oro y HOPG. Interesante fue el hecho de que en las break-juction unimoleculares de oro, se detectó un pico Kondo lo que indica que el momento magnético del radical PTM interactúa con los electrones de conducción. The present Doctoral Thesis is framed in the field of molecular electronics, specifically is focused on the development of new molecular electronic devices and on the study of the electron transfer phenomena associated to them. We exploit the properties of polychloro thriphenylmethyl radical (PTM) molecules to explore the charge transfer mechanisms involved in many different systems containing PTM derivatives. In the first part of the Thesis, we have described the study of the charge transfer process through two different families of molecular wires, oligo vinylene-thiophne (nTV) and fused oligo-p-phenylene vinylene (nCOPV), connecting two PTM moieties acting as electron donor/acceptor in mixed valence systems D-B-A. These systems were fully characterized by different spectroscopic techniques in their neutral, mixed valence and oxidized states. The mechanism for the intramolecular charge transfer through these wires was elucidated. In the second part of Thesis we have reported the synthesis of a family of PTM derivatives containing a thiol terminal group connected to the PTM through an alkyl chain with different length, able to form self-assembled monolayers (SAM) on gold substrates. We have studied the charge transport mechanisms through PTM SAMs contacted by eutectic gallium-indium electrode and scanning tunneling microcopy, in their different redox states. Finally, in last part of the thesis we have reported the study of the electric and magnetic properties of two PTM derivatives in gold and HOPG single molecule break-junctions. On gold PTM break-junctions, a Kondo peak was detected indicating that the localized magnetic moment of PTM radical interacts with conducting electrons.

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Iusan, Diana Mihaela. "Density Functional Theory Applied to Materials for Spintronics." Doctoral thesis, Uppsala universitet, Materialteori, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-119887.

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The properties of dilute magnetic semiconductors have been studied by combined ab initio, Monte Carlo, and experimental techniques. This class of materials could be very important for future spintronic devices, that offer enriched functionality by making use of both the spin and the charge of the electrons. The main part of the thesis concerns the transition metal doped ZnO. The role of defects on the magnetic interactions in Mn-doped ZnO was investigated. In the presence of acceptor defects such as zinc vacancies and oxygen substitution by nitrogen, the magnetic interactions are ferromagnetic. For dilute concentrations of Mn (~ 5%) the ordering temperature of the system is low, due to the short ranged character of the exchange interactions and disorder effects. The clustering tendency of the Co atoms in a ZnO matrix was also studied. The electronic structure, and in turn the magnetic interactions among the Co atoms, is strongly dependent on the exchange-correlation functional used. It is found that Co impurities tend to form nanoclusters and that the interactions among these atoms are antiferromagnetic within the local spin density approximation + Hubbard U approach. The electronic structure, as well as the chemical and magnetic interactions in Co and (Co,Al)-doped ZnO, was investigated by joined experimental and theoretical techniques. For a good agreement between the two, approximations beyond the local density approximation must be used. It is found that the Co atoms prefer to cluster within the semiconducting matrix, a tendency which is increased with Al co-doping. We envision that it is best to describe the system as superparamagnetic due to the formation of Co nanoclusters within which the interactions are antiferromagnetic. The magnetic anisotropy and evolution of magnetic domains in Fe81Ni19/Co(001) superlattices were investigated both experimentally, as well as using model spin dynamics. A magnetic reorientation transition was found.

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Knut, Ronny. "New Materials for Spintronics : Electronic structure and magnetism." Doctoral thesis, Uppsala universitet, Yt- och gränsskiktsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-167415.

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Materials exhibiting new functionalities due to interdependent electric (e.g. conductivity) and magnetic properties are potentially interesting for spintronics applications. We have investigated electronic and magnetic properties by means of x-ray spectroscopies and SQUID magnetometry in several magnetic materials, often in the form of thin films, which have shown promising properties for applications. One of the main subjects has been studies of inter-diffusion between layers in multilayer structures, which is an important factor for spin-dependent transport and magnetic properties. These studies have been performed by high kinetic (HIKE) photoemission spectroscopy where high photon energies increase the bulk sensitivity in comparison to soft x-ray photoemission spectroscopy. Cu/Ni multilayers were studied mainly as a model system and revealed a diffusion process that was dependent on layer thicknesses and capping materials. CoFeB/MgO/CoFeB, which is used as a magnetic field sensor in hard drives, has recently been shown to exhibit a perpendicular magnetic anisotropy (PMA) switchable by electric fields. We have studied both the interface quality and magnetic properties of thin CoFeB layers exhibiting PMA. Layered structures of full Heusler alloys Co2MnGe/Rh2CuSn have been proposed as a promising candidate for current-perpendicular-to-plane giant magneto-resistance sensors. Using HIKE,we have shown that diffusion of atoms, mainly Mn, occurs at temperatures lower than what is used in device fabrication, which likely contributes to the limited magneto-resistance values obtained. Lately, a large body of research has been performed on semiconductors doped with transition metal elements with the hope to find a ferromagnetic semiconductor at room temperature, a foundation for new devices combining spin and charge in their functionality. We have investigated Co and Fe doping in ZnO for different concentrations of the dopants and different annealing temperatures. The Co and Fe atoms are shown to forms clusters for which antiferromagnetic interactions are dominating.

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Satchell, Nathan David. "Hybrid superconducting/ferromagnetic thin films for super-spintronics." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15556/.

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This thesis examines the interaction between superconductivity and inhomogeneous ferromagnetism. Through careful engineering of the interface, it is possible to unlock a new spin aligned triplet Cooper pair, which is capable of penetrating and modifying the magnetisation of a ferromagnet in proximity to a singlet, s-wave, BCS, superconductor. This triplet state is the building block for the new class of super-spintronic devices. Two candidate ferromagnetic systems in which to study the spin aligned triplet are considered. Firstly, the rare-earth ferromagnet erbium is fabricated using sputter deposition. Neutron diffraction measurements show the retention of the conical magnetic state in the thin film form for the first time. This conical state makes it an ideal candidate material for triplet Cooper pair generation. Placing erbium next to superconducting niobium has a drastic effect on the critical temperature of the superconductor, causing a suppression and oscillation of Tc with erbium thickness. In addition the remanent state of erbium at a single thickness can be used as a control to switch the niobium from the superconducting state into the normal state. The second system studied is the superconducting spin valve. In this system the inhomogeneity is engineered in a multi-layer structure using exchange biased Co. To study the nature and extent of the triplet Cooper pair in this structure, large scale facility techniques are employed to look for expected changes to the magnetic state of the heterostructure, with the onset of superconductivity. Surprisingly, no observation directly attributable to the triplet Cooper pair was observed. Instead a new type of induced ferromagnetism in a normal metal coupled to the superconducting spin valve was discovered.

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Huang, Lunmei. "Computational Material Design : Diluted Magnetic Semiconductors for Spintronics." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7800.

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Gangmei, Prim. "Magnetisation dynamics of nanoscale magnetic materials and spintronics." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3502.

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The magnetisation dynamics of a single square nanomagnet, the interaction between a pair of nanodiscs, a partially built writer structure and a range of magnetic tunnel junction sensor heads were studied using Time Resolved Scanning Kerr Microscopy (TRSKM) and four probe contact DC electrical transport measurements. Large amplitude magnetisation dynamics of a single square nanomagnet have been studied by TRSKM. Experimental spectra revealed that only a single mode was excited for all bias field values. Micromagnetic simulations demonstrate that at larger pulsed field amplitudes the center mode dominates the dynamic response while the edge mode is almost completely suppressed. The magnetisation dynamics occurring in a system comprised of two laterally separated magnetic nano-discs were also investigated. The polar Magneto-Optical Kerr Effect was used to measure the dynamic response of each disc independently so as to demonstrate that dynamic dipolar interactions between non-uniform spin wave modes in the different discs may be identified from the difference in their phase of oscillation. Results show a stronger dynamic dipolar interaction than expected from micromagnetic simulations highlighting both the need for characterisation and control of magnetic properties at the deep nanoscale and the potential use of dynamic interactions for the realization of useful magnetic nanotechnologies. TRSKM measurements were made simultaneously of the three Cartesian components of the magnetisation vector, by means of a quadrant photodiode polarisation bridge detector, on partially built hard disk writer structures. The rise time, relaxation time, and amplitude of each component has been related to the magnetic ground state, the initial torque, and flux propagation through the yoke and pole piece. Dynamic images reveal “flux-beaming” in which the magnetisation component parallel to the symmetry axis of the yoke is largest along that axis. A comparison of the magnetisation dynamics excited with different pulsed excitation amplitudes was also made. The results shows that more effective flux beaming is observed for higher pulse amplitudes. Lastly the microwave emission of Tunnel Magnetoresistance (TMR) nanopillars has been measured using a four probe contact DC electrical transport measurement technique as a magnetic field is applied in the plane of the film at different angles (ϕ_H ) with respect to the easy axis. Experimental spectra revealed that a more complicated spectrum containing several modes is observed as ϕ_H is increased. The modes were identified as edge and higher order modes from the statistical distribution of modes from different devices and micromagnetic simulations. The in-plane and out-of-plane components of the Spin Transfer Torque (STT) were estimated by analytical fitting of experimental data for the lowest frequency edge mode for the value of ϕ_H where the amplitude of the said mode was a maximum and its frequency a minimum. The estimated values are larger than expected perhaps due to the macrospin approximation made in deriving the analytical model. The results presented in this thesis can contribute to the understanding of magnetisation dynamics in industrially relevant data storage devices as well as the realization of a dipolar field coupling mechanism for arrays of nanooscillators.

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Huskisson, David. "Structural characterisation of L10 ordered materials for spintronics." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/structural-characterisation-of-l10-ordered-materials-for-spintronics(6328cc71-a0e6-42a8-b6e1-92e0c9ea9b2a).html.

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L10 ordered materials offer considerable promise for enhancing the performance of current and future spintronic technologies, particularly magnetic data storage. The need for greater areal density fuels research into high anisotropy materials, such as L10 ordered FePt. MnAl is another L10 ordered material which has great potential as an efficient spin polariser for the development of magnetic tunnel junctions due to its low spin-orbit coupling. The magnetic properties of these materials depend on their crystal structure and degree of ordering. The work presented here concerns the structural characterisation of L10 ordered materials and the development of L10 ordered MnAl thin films. The additional parameter space offered by remote plasma sputtering was explored with a view to controlling the grain size of FePt thin films by varying the target bias voltage. A semi-automatic grain identification method was identified, improving the repeatability and reliability of the results. The average grain size and grain size distribution was found to increase after annealing, but was robust against variation in the target bias voltage. The structural properties of FeRh were investigated as a complementary material for next generation magnetic data storage applications. Island type growth was seen with considerable dewetting from the substrate. The degradation of the magnetic properties of these films with decreasing thickness was attributed to the decrease in crystal order as observed in this work. MnAl thin films were fabricated by co-sputtering. The formation of the metastable L10 phase was found to be highly sensitive to the elemental composition and processing temperatures used. Local ordering was observed which improved after annealing to give a maximum saturation magnetisation of 67 emu/cm3 . This work provides a strong grounding in the challenges associated with producing ferromagnetic, L10 ordered thin films of MnAl, and identifies directions for further research.

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Lu, Yu. "DEVELOPMENT OF NEW OGANIC-BASED MAGMENTS FOR SPINTRONICS." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440153101.

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Bakkar, Said. "NEW INVERSE-HEUSLER MATERIALS WITH POTENTIAL SPINTRONICS APPLICATIONS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2207.

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Spintronics or spin-electronics attempt to utilize the electronic spin degree of freedom to make advanced materials and devices for the future. Heusler materials are considered very promising for spintronics applications as many highly spin-polarized materials potentially exist in this family. To accelerate materials discovery and development, The Materials Genome Initiative (https://www.mgi.gov/) was undertaken in 2011 to promote theory-driven search of new materials. In this thesis work, we outline our effort to develop several new materials that are predicted to be 100% spin-polarized (half-metallic) and thermodynamically stable by theory. In particular, two Mn-based Heusler families were investigated: Mn2CoZ (Z= Ga, Sb, Ge) and Mn2FeZ (Z=Si,Ge), where the latter is potentially a new Heusler family. These materials were synthesized using the arc-melting technique and their crystal structure was investigated using the X-ray diffraction (XRD) method before and after appropriate annealing of the samples. Preliminary magnetometry measurements are also reported. We first developed a heat-treatment procedure that could be applied to all the Mn-based compounds mentioned above. Mn2CoGa was successfully stabilized in the cubic inverse-Heusler phase with a=5.869 Å and magnetic moment of 2.007 /fu. This is in good agreement with prior literature reports [1]. However, cubic phases of Mn2CoSb and Mn2CoGe could not be stabilized within the annealing temperature range that is accessible in our lab. We successfully synthesized a cubic Mn2FeSi phase using an annealing procedure similar to Mn2CoGa. The measured cubic lattice parameter of Mn2FeSi was 5.682 Å. This is the first experimental report of this material to the best of our knowledge. Detailed analysis of relative intensities of different X-ray peaks revealed that the structure is most likely in an inverse Heusler phase, in agreement with theory. However, a substantial atomic-level disorder was also uncovered from XRD analysis that requires further investigation to understand its effect on its magnetism and half-metallicity. Mn2FeGe showed the existence of non-cubic phases that substantially weakened at high annealing temperatures.

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Huang, Biqin. "Vertical transport silicon spintronic devices." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 201 p, 2008. http://proquest.umi.com/pqdweb?did=1459914011&sid=17&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Galassi, Fabio. "Fabrication of high-k dielectric thin films for spintronics." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10449/.

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Lo scopo di questa tesi è la fabbricazione di ossidi complessi aventi struttura perovskitica, per mezzo della tecnica Channel Spark Ablation (CSA). Più precisamente sono stati depositati film sottili di manganite (LSMO), SrTiO3 (STO) e NdGaO3 (NGO). Inoltre nel laboratorio ospite è stata effettuata la caratterizzazione elettrica e dielettrica (spettroscopia di impedenza), mentre per l'analisi strutturale e chimica ci si è avvalsi di collaborazioni. Sono stati fabbricati dispositivi LSMO/STO/Co e se ne è studiato il comportamento magnetoresistivo e la bistabilità elettrica a seconda del carattere epitassiale od amorfo dell'STO. I risultati più promettenti sono stati ottenuti con STO amorfo. Sono stati costruiti diversi set di condensatori nella configurazione Metallo/Isolante/Semiconduttore (MIS), con M=Au, I=STO o NGO ed S=Nb:STO, allo scopo di indagare la dipendenza delle proprietà dielettriche ed isolanti dai parametri di crescita. In particolare ci si è concentrati sulla temperatura di deposizione e, nel caso dei film di STO, anche sulla dipendenza della costante dielettrica dallo spessore del film. Come ci si aspettava, la costante dielettrica relativa dei film di STO (65 per un film spesso 40 nm e 175 per uno di 170 nm) si è rivelata maggiore di quella dei film di NGO per i quali abbiamo ottenuto un valore di 20, che coincide con il valore del bulk. Nonostante l'elevata capacità per unità di area ottenibile con l'STO, la costante dielettrica di questo materiale risulta fortemente dipendente dallo spessore del film. Un ulteriore aspetto critico relativo all'STO è dato dal livello di ossidazione del film: le vacanze di ossigeno, infatti, possono ridurre la resistività dell'STO (nominalmente molto elevata), ed aumentarne la corrente di perdita. Al contrario l'NGO è meno sensibile ai processi tecnologici e, allo stesso tempo, ha un valore di costante dielettrica più alto rispetto ad un tipico dielettrico come l'ossido di silicio.

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Fu, Lei. "Spintronic sensor based microwave imaging." AIP Publishing, 2012. http://hdl.handle.net/1993/31646.

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Novel characteristics of spin-based phenomena are intensively researched in the hope of discovering effects that could be used to develop new types of high-performance spintronic devices. Recent dynamics studies have revealed new principles for spintronic devices to sense microwaves. The capabilities for detecting both microwave electric field and magnetic field could make the spintronic microwave sensor as ubiquitous as semiconductor devices in microwave applications in the future. In this thesis, the feasibility of spintronic sensors in microwave applications has been researched and developed. Thanks to the high conversion efficiency of microwave rectification in the magnetic tunnel junction (MTJ) based spintronic sensor, it can directly measure the coherent spatially scattered microwave field distribution and detect a hidden object by analyzing the reflected microwave amplitude pattern. To enable the “real-time” vector measurement of the microwave field, a sensor based rapid phase detection technique is also developed. Combining the rapid phase detection technique and the microwave holography principle, a two-dimensional microwave holographic imaging system using a spintronic sensor was built. The high sensitivity of the microwave phase measurement allows the coherent imaging of the target to be reconstructed in noisy environments. By adapting the broadband measurement, not only the shape but also the distance of the target can be determined, which implies that three-dimensional imaging is achievable using a spintronic device. Combining the broadband microwave measurement and a wavefront reconstruction algorithm with a spintronic microwave sensor in circular trajectory, the reconstructed images of targets are obtained. The reconstructed images clearly indicate the targets' positions even when the targets were immersed in a liquid to simulate an inhomogeneous tissue environment. Our spintronic techniques provide a promising approach for microwave imaging, with the potential to be used in various areas, such as biomedical applications, security services, and material characterization. October 2016

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Kirby, Brian J. "Annealing-dependent phenomena in Ga₁[-x]Mn[x]As." Diss., Columbia, Mo. : University of Missouri-Columbia, 2004. http://hdl.handle.net/10355/4091.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2004. Bracketed information should be subscripted. The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 29, 2006) Vita. Includes bibliographical references.

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Benini, Mattia. "Investigations of ferromagnet-organic bilayers for application in spintronics." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15788/.

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La spintronica è una branca dell’elettronica che sfrutta oltre alla carica, lo spin dell’elettrone per il trasporto dell'informazione. Il dispositivo spintronico modello, chiamato spin valve, è costituito da strati ferromagnetici disaccoppiati tra loro attraverso un materiale non magnetico di diversa natura. Più recentemente il campo della spintronica si è orientato verso l’uso di semiconduttori organici come materiali non magnetici dando origine alla cosiddetta “organic spintronics”. Dopo i primi successi di integrazione di materiali organici in dispositivi spintronici, sono emerse alcune peculiarità dei comportamenti magnetoresistivi che indicano come le molecole giochino un ruolo maggiore rispetto al mero trasporto di correnti spin-polarizzate. A questo concetto è stato associato al termine spinterface. Questo nuovo tipo di interfacce è di notevole interesse in molteplici campi oltre la spintronica, come l’optoelettronica o le memorie magnetiche. In questo lavoro di tesi si sono studiate proprietà magnetiche di bistrati cobalto/fullerene e cobalto/gallio-quinolina, con l’obiettivo di verificare il ruolo del materiale organico nella definizione delle proprietà magnetiche dello strato di cobalto, con l’obiettivo di verificare la presenza di effetti di “spinterface”.

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Carlegrim, Elin. "Development of Organic-Based Thin Film Magnets for Spintronics." Doctoral thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-56262.

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In the growing field of spintronics, development of semiconducting magnets is a high priority. Organic-based molecular magnets are attractive candidates since their properties can be tailor-made by organic chemistry. Other advantages include low weight and low temperature processing. Vanadium tetracyanoethylene, V(TCNE)x, x~2, is particularly interesting since it is one of very few semiconducting magnets with magnetic ordering above room temperature. The aim of the research presented in this thesis was to prepare and characterize thin film organic-based magnets with focus on V(TCNE)x. Photoelectron and absorption spectroscopy studies were performed leading to a more complete picture of the electronic and chemical structure of the material. Depending on the preparation method of V(TCNE)x, the material contains varying amounts of disorder which among other things makes it very air sensitive. In this thesis, a new preparation method for organic-based magnets based on physical vapor deposition is presented and the first result shows that it generates less air sensitive V(TCNE)x than previous methods reported. A new spin valve design based on V(TCNE)x was proposed where the material delivers both spin-filtering and spin-transporting functionality, making use of its fully spin-polarized transport levels. In such devices, the interface of V(TCNE)x with ferromagnetic metals is of great importance and was hence studied. As vanadium ions always are very reactive towards oxygen, substituting vanadium by a less reactive ion would be desirable from both an interface engineering and device packaging perspective. Very few alternatives exist however that orders magnetically above room temperature. In order to find out what are the key design criteria for preparing thin film semiconducting room temperature magnets, we have begun to study systems which order magnetically much below room temperature and compared them with V(TCNE)x.

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Studniarek, Michal. "Interface and multifunctional device spintronics : studies with synchrotron radiation." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE028/document.

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La spintronique multifonctionnelle est une nouvelle direction d'avancement pour aller au-delà des limites de l'électronique moderne. Il vise à développer des dispositifs qui seraient sensibles à plus d’un stimulus et/ou ont un signal multi-réponse. Dans cette thèse, nous explorons cette voie multifonctionnelle émergente en combinant l’électronique de spin et les systèmes organiques pour ouvrir la voie vers des dispositifs polyvalents. Nous étudions la formation d'une spinterface dans le système Co/manganèse-phthalocyanine. Nous proposons l'introduction de multifonctionnalités intrinsèques en utilisant des matériaux à transition de spin. Nous développons une nouvelle approche de fonctionnalisation pour ajuster leurs propriétés vers des applications. Nous proposons un contrôle fonctionnel externe sur une spinterface en utilisant un substrat multiferroïque. Dans le cadre de cette thèse, un insert polyvalent à température variable a été développé à la ligne de lumière DEIMOS du synchrotron SOLEIL. Nous démontrons comment il peut être utilisé pour sonder des atomes actifs dans n'importe quel dispositif électronique Multifunctional spintronics is a new direction of advancement beyond the limits of modern electronics. By combining elementary charge of an electron and its spin, it aims to develop devices which would be sensitive to more than one stimuli and/or have multiresponse signal. In this thesis, we explore the multifunctional potential emerging while combining spin electronic and organic systems to pave the way towards multipurpose devices. First, we study formation of a ferromagnetic/organic spinterface in Co/manganese-phthalocyanine system. We propose introduction of intrinsic multifunctionality by using spin crossover materials. We develop a novel functionalization approach for tuning their properties towards device applications. We propose an external functional control over any hybrid spinterface by using multiferroic substrate. In the framework of this thesis, a Versatile Variable Temperature Insert was developed at the DEIMOS beamline of the SOLEIL synchrotron. We demonstrate how it can be used to probe active atoms in any microelectronic device

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Galbiati, Marta. "Molecular Spintronics : from Organic Semiconductors to Self-Assembled Monolayers." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112158/document.

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Cette thèse s’inscrit dans le domaine de la spintronique moléculaire. Elle s’intéresse plus précisément aux nouvelles opportunités de façonnage de la polarisation de spin qui découlent de l'hybridation métal ferromagnétique/molécule à l'interface : le nouveau concept de « spinterface ».Dans une première partie nous présentons l’étude de nanojonctions tunnel magnétiques à base de monocouches auto-assemblées (SAMs). Ce système est un des plus prometteur dans l’optique de moduler les propriétés des dispositifs de spintronique par ingénierie chimique, tel un LEGO moléculaire. Nous y présentons la fonctionnalisation de la manganite demi-métallique (La,Sr)MnO3 (LSMO) avec des SAMs d’acides alkylphosphoniques et la fabrication de nanojonctions LSMO/SAMs/Co avec une surface de quelque 10 nm2. Une magnétorésistance de 30% à 50% est observée dans la majorité des dispositifs avec une magnétorésistance tunnel (TMR) jusqu'à 250 % à basse température. Un point remarquable est aussi le comportement très robuste du signal avec la tension: environ 20% de TMR est encore observée au-dessus d’une tension de 1 V. L'influence de la longueur de la chaîne moléculaire a été aussi étudiée et représente un premier pas vers la modulation des dispositifs au niveau moléculaire. Dans une deuxième partie nous présentons l’étude des dispositifs organiques à base de métaux ferromagnétiques à haute TC (température de Curie) et semi-conducteurs organiques. Nous avons réalisé des vannes de spin de Co/Alq3/Co avec des sections de 50 ou 100 µm et fabriquées in-situ par « shadow mask ». Des mesures à température ambiante ont permis d’observer -4% de magnétorésistance (MR) dans une vanne de spin Co/Alq3/Co et +8% MR dans une vanne de spin de Co/MgO/Alq3/Co. Le rôle des deux interfaces sur les propriétés de polarisation de spin des dispositifs est aussi étudié et détaillé. Une forte hybridation métal/molécule dépendant du spin à l'interface inferieure de Co/Alq3, présentant un effet de spinterface (inversion de la polarisation en spin), est observée. Ces études montrent que les effets de spinterface, comme l’inversion de la polarisation de spin, peuvent persister dans un dispositif jusqu’à température ambiante This thesis targets the field of molecular spintronics and more particularly the new spin polarization tailoring opportunities, unachievable with inorganic materials, which arise from the ferromagnetic metal/molecule hybridization at the interface.: the new concept of Spinterface.In a first part we investigate Self-Assembled Monolayers (SAMs) based magnetic tunnel nanojunctions. This system appears to be a highly promising candidate to engineer the properties of spintronics devices at the molecular level since SAMs are the equivalent of a molecular LEGO building unit. We present the functionalization of the half-metallic manganite (La,Sr)MnO3 (LSMO) with alkyl phosphonic acids SAMs and the fabrication of LSMO/SAMs/Co magnetic tunnel nanojunctions with an area of few 10 nm2. MR of 30% to 50% is observed in most of the devices, while we report even up to 250% tunnel magnetoresistance (TMR) at low temperature. The most striking point is the robustness of the signal with bias voltage with still 20% TMR observed in the volt range. The influence of the molecular chain length is also investigated and represents a first step towards achieving molecular tailoring.In a second part we develop organic spintronics devices relying on high Curie temperature metallic ferromagnetic electrodes and standard organic semiconductor such as Co/Alq3/Co organic spin valves (OSVs). Junctions have a large area (section of 50 or 100 µm) and are fabricated in-situ by shadow mask. Magnetoresistance (MR) effects at room temperature are investigated with -4% MR observed in Co/Alq3/Co OSVs and +8% MR in Co/MgO/Alq3/Co OSVs. The role of the two interfaces on the spin polarization properties of the devices is also investigated. A stronger spin-dependent hybridization is found to occur at the bottom Co/Alq3 interface inverting the spin polarization on the first molecular layer. The observation of spin polarization inversion at room temperature demonstrates that spinterface effects can strive up to room temperature

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SOARES, GABRIEL. "Magnetization dynamics and spintronics of soft magnetic thin films." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2841180.

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Gustavsson, Fredrik. "Properties of Fe/ZnSe Heterostructures : A Step Towards Semiconductor Spintronics." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2002. http://publications.uu.se/theses/91-554-5314-7/.

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Warren, Jack. "Fabrication and characterisation of novel materials and devices for spintronics." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/fabrication-and-characterisation-of-novel-materials-and-devices-for-spintronics(ac352bea-9068-4642-9fa8-f7412881463b).html.

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The spintronic materials graphene and FeRh are of great scientific and technological interest due to their unique properties. Graphene's remarkable electronic transport and low spin interaction suggest it could be a near-perfect spin-transport material, while the equiatomic alloy FeRh undergoes a first-order antiferromagnetic (AF) to ferromagnetic (FM) phase transition when heated through a critical temperature ~370 K. Combining these materials could lead to a single multifunctional spin injection, transport and detection device in which a range of stimuli - heat, magnetic field, strain etc. - could be used to manipulate the device state. However, realisation of such a multifunctional device is extremely challenging. This thesis describes the progress made in developing a novel method of spin injection into graphene, and details a study of the metamagnetic phase transition in FeRh nanowires suitable for use as spin injection and detection electrodes. The measured values of spin lifetime and spin diffusion length in graphene are an order of magnitude lower than those predicted theoretically. In this project, a novel 1D contact geometry was investigated to determine whether the dwelling of spins underneath tunnel barrier contacts was the cause of the discrepancy. Although these devices exhibited very high charge carrier mobility - indicating successful device fabrication, defect-free graphene flakes and low levels of contamination - no spin signals were observed. Through a thorough investigation of this unexpected result it was determined that the quality of the graphene/- ferromagnetic interface was limiting the polarisation of injected spin current. The use of FeRh as a novel spin injection and detection material was investigated through magnetic force microscopy imaging of the AF and FM phases during heating and cooling sweeps. The results from FeRh full-films showed a strong dependence on surface morphology, as certain surface types were observed to favour the FM phase. These behaviours were confirmed in patterned nanowire devices, which indicated that the dependence on surface topology dominated over spatial confinement effects. In order to perform these studies a magneto-transport measurement system capable of performing measurements over a wide temperature range 2 K - 500 K in a rotatable magnetic field of up to 750 mT was developed. The noise base of the completed system was measured at just 10% above the theoretical minimum level.

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Kao, Chi-Yueh. "Thin films of organic-based magnetic semiconductors for organic spintronics." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343748166.

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Gallagher, James C. "Synthesis and Investigation of High Quality Materials for Spintronics Applications." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469141590.

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Roy, Kuntal. "Hybrid spintronics and straintronics: An ultra-low-energy computing paradigm." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/381.

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The primary obstacle to continued downscaling of charge-based electronic devices in accordance with Moore's law is the excessive energy dissipation that takes place in the device during switching of bits. Unlike charge-based devices, spin-based devices are switched by flipping spins without moving charge in space. Although some energy is still dissipated in flipping spins, it can be considerably less than the energy associated with current flow in charge-based devices. Unfortunately, this advantage will be squandered if the method adopted to switch the spin is so energy-inefficient that the energy dissipated in the switching circuit far exceeds the energy dissipated inside the system. Regrettably, this is often the case, e.g., switching spins with a magnetic field or with spin-transfer-torque mechanism. In this dissertation, it is shown theoretically that the magnetization of two-phase multiferroic single-domain nanomagnets can be switched very energy-efficiently, more so than any device currently extant, leading possibly to new magnetic logic and memory systems which might be an important contributor to Beyond-Moore's-Law technology. A multiferroic composite structure consists of a layer of piezoelectric material in intimate contact with a magnetostrictive layer. When a tiny voltage of few millivolts is applied across the structure, it generates strain in the piezoelectric layer and the strain is transferred to the magnetostrictive nanomagnet. This strain generates magnetostrictive anisotropy in the nanomagnet and thus rotates its direction of magnetization, resulting in magnetization reversal or 'bit-flip'. It is shown after detailed analysis that full 180 degree switching of magnetization can occur in the "symmetric" potential landscape of the magnetostrictive nanomagnet, even in the presence of room-temperature thermal fluctuations, which differs from the general perception on binary switching. With proper choice of materials, the energy dissipated in the bit-flip can be made as low as one attoJoule at room-temperature. Also, sub-nanosecond switching delay can be achieved so that the device is adequately fast for general-purpose computing. The above idea, explored in this dissertation, has the potential to produce an extremely low-power, yet high-density and high-speed, non-volatile magnetic logic and memory system. Such processors would be well suited for embedded applications, e.g., implantable medical devices that could run on energy harvested from the patient's body motion.

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Bonhomme, Phillip. "Circuit modeling of spintronic devices: a SPICE implementation." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51818.

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Every engineer that has worked on designing an integrated circuit has to leverage an under- standing of device physics. Understanding device physics is essential when optimizing a design for speed, power, etc. These characteristics affect the bottom line when considering an integrated circuit used in a particular application. In order for there to be an under- standing of device physics, there must be a device model that is developed for a device of interest. The development of a device model often involves utilizing fundamental physical equations in a manner that is solvable by either analytical or numerical means. This typically begins by simplifying fundamental physical equations, possibly spanning multiple domains, and considering the physical quantities of interest. In order to make simplifications, assumptions about the underlying physics must be made. It is the process of transitioning from known physics laws to simplified mathematical models that a device modeler spans. This thesis will cover the device modeling aspects of a new classification of computing devices, spintronics. It will begin by stating the physical assumptions necessary for the operation of spintronic devices. Then it will go the process of deriving the underlying physical equations and stating them in a tractable form with the appropriate boundary conditions. Then these equations will be manipulated and mapped into an equivalent circuit. The equivalent circuits will them be validated against analytical solutions provided from other works. It will then finish by providing example devices that can be simulated with the develop device models, and some optimization results are proposed based off a simplified circuit model.

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Lee, Soobeom. "Study on Electrical Generation and Manipulation of Spin Current in n-type Si Spin MOSFET." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263671.

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Phillips, Lee Charles. "Spintronic devices with highly spin-polarised manganite electrodes and graphene channels." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610490.

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