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Magneto And Spin Transport In Magnetically Doped Semiconductors And Magnetic Insulators
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Book Synopsis Magneto and Spin Transport in Magnetically Doped Semiconductors and Magnetic Insulators by : Zihao Yang
Download or read book Magneto and Spin Transport in Magnetically Doped Semiconductors and Magnetic Insulators written by Zihao Yang and published by . This book was released on 2017 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last two decades, spin transistors that operate using both charge and spin properties of electrons have motivated extensive studies of injection, detection and manipulation of electronic spin current in various material systems. Dilute magnetic semiconductors, in which the spin polarized charge carriers are coupled to the magnetic moment, are of particular interest due to their compatible lattice structures and similar growth methods to current Si and GaAs technology. The first part of this thesis focuses on the structural, magnetic and magnetotransport properties of magnetically doped GaN and 2D MoS2. The Gd doped AlN/GaN heterostructures are grown by plasma assisted molecular beam epitaxy. The Gd atoms are [delta]-doped at the AlN/GaN heterointerface where the two dimensional electron gas (2DEG) forms. These samples exhibit defect-induced room temperature ferromagnetism with an easy axis along the c-axis. However, the nonlinear Hall resistivity does not track the magnetization in these Gd doped samples indicating the lack of coupling between the conduction electrons in the 2DEG and the Gd-induced ferromagnetism. This makes Gd doped GaN not useful as a dilute magnetic semiconductor. Mn doped few-layer MoS2 samples synthesized via sulfurization of Mn thin film on sapphire are fabricated in the aim of realizing a 2D dilute magnetic semiconductor. However, these samples mainly show paramagnetism implying the lack of ferromagnetic coupling between the Mn dopants.
Download or read book Spin Current written by Sadamichi Maekawa and published by Oxford University Press. This book was released on 2017 with total page 541 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a new branch of physics and technology, called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called "spin current", are manipulated and controlled together. This book is intended to provide an introduction and guide to the new physics and applications of spin current.
Book Synopsis Transport Studies of the Electrical, Magnetic and Thermoelectric properties of Topological Insulator Thin Films by : Jinsong Zhang
Download or read book Transport Studies of the Electrical, Magnetic and Thermoelectric properties of Topological Insulator Thin Films written by Jinsong Zhang and published by Springer. This book was released on 2016-04-18 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the transport studies of topological insulator thin films grown by molecular beam epitaxy. Through band structure engineering, the ideal topological insulators, (Bi1−xSbx)2Te3 ternary alloys, are successfully fabricated, which possess truly insulating bulk and tunable conducting surface states. Further transport measurements on these ternary alloys reveal a disentanglement between the magnetoelectric and thermoelectric properties. In magnetically doped topological insulators, the fascinating quantum anomalous Hall effect was experimentally observed for the first time. Moreover, the topology-driven magnetic quantum phase transition was Systematically controlled by varying the strength of the spin-orbital coupling. Readers will not only benefit from the description of the technique of transport measurements, but will also be inspired by the understanding of topological insulators.
Book Synopsis Topological Insulator Systems with Magnetism by : Joon Lee
Download or read book Topological Insulator Systems with Magnetism written by Joon Lee and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes topological insulator systems hybridized with magnetism. The Dirac surface states induced by strong spin-orbit interaction can be modified by breaking time-reversal symmetry that protects the surface state. We study the modified surface states of topological insulators by introducing magnetism by doping magnetic atoms or interfacing a magnetic layer to the surface. Also, we explore potential spintronics applications of topological insulators by utilizing magnetic tunnel junctions to evidence the inherently spin-polarized texture of the topological insulator surface state. For this dissertation research, single crystalline topological insulator thin films grown by molecular beam epitaxy have been employed. From the motivation of breaking time-reversal symmetry in the surface state, the first experiments study the structural, magnetic, and magneto-transport properties of a magnetically doped, three-dimensional topological insulator, bismuth telluride doped with Mn. We observed ferromagnetism with a Curie temperature up to 17 K in films with ~2-10% Mn concentrations. The observed ferromagnetism is independent of carrier density in the Mn-doped bismuth telluride films, suggesting that it is not mediated by charge carriers. The next topological insulator system with magnetism is a hybrid topological insulator/ferromagnet heterostructure as a new approach for topological insulator hybrid systems using a dilute magnetic semiconductor Ga1-xMnxAs. A highly resistive Ga1-xMnxAs with out-of-plane magnetic anisotropy is cleanly interfaced with a topological insulator Bi2-xSbxTe3-ySey by molecular beam epitaxy. Magneto-transport measurements on a top-gated heterostructure device show a crossover from positive magneto-conductance to negative magneto-conductance as well as a systematic emergence of an anomalous Hall effect as the temperature is lowered or as the chemical potential approaches the Dirac point. The results are possibly interpreted as the modification of the surface state at the interface by the adjacent, ferromagnetic Ga1-xMnxAs layer. The last topological insulator system with magnetism is a topological insulator channel with a magnetic tunnel junction on it. We seek a potential role of topological insulators in spintronics as generators of carrier spin polarization. Electrical detection of the inherent spin polarization of the topological insulator surface state was demonstrated using a permalloy/Al2O3 magnetic tunnel junction on a (Bi,Sb)2Te3 channel. The observed hysteretic spin signals occurring at the magnetic switching field of the ferromagnet permalloy layer can be interpreted as the projection of the current-induced spin polarization on a topological insulator surface onto the magnetization of the ferromagnet via tunneling.
Book Synopsis Quantized Phenomena of Transport and Magneto-Optics in Magnetic Topological Insulator Heterostructures by : Masataka Mogi
Download or read book Quantized Phenomena of Transport and Magneto-Optics in Magnetic Topological Insulator Heterostructures written by Masataka Mogi and published by Springer Nature. This book was released on 2022-05-07 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents experimental studies on emergent transport and magneto-optical properties in three-dimensional topological insulators with two-dimensional Dirac fermions on their surfaces. Designing magnetic heterostructures utilizing a cutting-edge growth technique (molecular beam epitaxy) stabilizes and manifests new quantization phenomena, as confirmed by low-temperature electrical transport and time-domain terahertz magneto-optical measurements. Starting with a review of the theoretical background and recent experimental advances in topological insulators in terms of a novel magneto-electric coupling, the author subsequently explores their magnetic quantum properties and reveals topological phase transitions between quantum anomalous Hall insulator and trivial insulator phases; a new topological phase (the axion insulator); and a half-integer quantum Hall state associated with the quantum parity anomaly. Furthermore, the author shows how these quantum phases can be significantly stabilized via magnetic modulation doping and proximity coupling with a normal ferromagnetic insulator. These findings provide a basis for future technologies such as ultra-low energy consumption electronic devices and fault-tolerant topological quantum computers.
Book Synopsis Transport Studies of Mesoscopic and Magnetic Topological Insulators by : Abhinav Kandala
Download or read book Transport Studies of Mesoscopic and Magnetic Topological Insulators written by Abhinav Kandala and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological Insulators (TI) are a novel class of materials that are ideally insulating in the bulk, but have gapless, metallic states at the surface. These surface states have very exciting properties such as suppressed backscattering and spin-momentum locking, which are of great interest for research efforts towards dissipation-less electronics and spintronics. The popular thermo-electrics from the Bi chalcogenide family -- Bi2Se3 and Bi2Te3 -- have been experimentally demonstrated to be promising candidate TI materials, and form the chosen material system for this dissertation research. The first part of this dissertation research focuses on low temperature magneto-transport measurements of mesoscopic topological insulator devices (Chapter 3). The top-down patterning of epitaxial thin films of Bi2Se3 and Bi2Te3 (that are plagued with bulk conduction) is motivated, in part, by an effort to enhance the surface-to-volume ratio in mesoscopic channels. At cryogenic temperatures, transport measurements of these devices reveal periodic conductance fluctuations in straight channel devices, despite the lack of any explicit patterning of the TI film into a ring or a loop. A careful analysis of the surface morphology and comparison with the transport data then demonstrate that scattering off the edges of triangular plateaus at the surface leads to the creation of Aharonov-Bohm electronic orbits responsible for the periodicity. Another major focus of this dissertation work is on combining topological insulators with magnetism. This has been shown to open a gap in the surface states leading to possibilities of magnetic "gating" and the realization of dissipation-less transport at zero-field, amongst several other exotic quantum phenomena. In this dissertation, I present two different schemes for probing these effects in electrical transport devices -- interfacing with insulating ferromagnets (Chapter 4) and bulk magnetic doping (Chapter 5). In Chapter 4, I shall present the integration of GdN with Bi2Se3 thin films. Careful structural, magnetic and electrical characterization of the heterostructures is employed to confirm that the magnetic species is solely restricted to the surface, and that the ferromagnetic GdN layer to be insulating, ensuring current flow solely through the TI layer. We also devise a novel device geometry that enables direct comparison of the magneto-transport properties of TI films with and without proximate magnetism, all, in a single device. A comparative study of weak anti-localization suggested that the overlying GdN suppressed quantum interference in the top surface state. In our second generation hetero-structure devices, GdN is interfaced with low-carrier density, gate-tunable thin films of (Bi,Sb)2Te3 grown on SrTiO3 substrates. These devices enable us to map out the comparison of magneto-transport, as the chemical potential is tuned from the bulk conduction band into the bulk valence band.In a second approach to study the effects of magnetism on TI's, I shall present, in Chapter 5, our results from magnetic doping of (Bi,Sb)2Te3 thin films with Cr -- a system that was recently demonstrated to be a Quantum Anomalous Hall (QAH) insulator. In a Cr-rich regime, a highly insulating, high Curie temperature ferromagnetic phase is achieved. However, a careful, iterative process of tuning the composition of this complex alloy enabled access to the QAHE regime, with the observation of near dissipation-less transport and perfect Hall quantization at zero external field. Furthermore, we demonstrate a field tilt driven crossover between a quantum anomalous Hall phase and a gapless, ferromagnetic TI phase. This crossover manifests itself in an electrically tunable, giant anisotropic magneto-resistance effect that we employ as a quantitative probe of edge transport in this system.
Book Synopsis Introduction to the Physics of Diluted Magnetic Semiconductors by : Jan A. Gaj
Download or read book Introduction to the Physics of Diluted Magnetic Semiconductors written by Jan A. Gaj and published by Springer Science & Business Media. This book was released on 2011-01-12 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: As materials whose semiconducting properties are influenced by magnetic ions, DMSs are central to the emerging field of spintronics. This volume focuses both on basic physical mechanisms (e.g. carrier-ion and ion-ion interactions), and resulting phenomena.
Download or read book Spintronics written by Tomasz Dietl and published by Academic Press. This book was released on 2009-02-12 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt: This new volume focuses on a new, exciting field of research: Spintronics, the area also known as spin-based electronics. The ultimate aim of researchers in this area is to develop new devices that exploit the spin of an electron instead of, or in addition to, its electronic charge. In recent years many groups worldwide have devoted huge efforts to research of spintronic materials, from their technology through characterization to modeling. The resultant explosion of papers in this field and the solid scientific results achieved justify the publication of this volume. Its goal is to summarize the current level of understanding and to highlight some key results and milestones that have been achieved to date. Semiconductor spintronics is expected to lead to a new generation of transistors, lasers and integrated magnetic sensors that can be used to create ultra-low power, high-speed memory, logic and photonic devices. In addition, development of novel devices such as spin-polarized light emitters, spin field effect transistors, integrated sensors and high-temperature electronics is anticipated. Spintronics has emerged as one of the fastest growing areas of research This text presents an in-depth examination of the most recent technological spintronic developments Includes contributions from leading scholars and industry experts
Book Synopsis Charge and Spin Transport in Dilute Magnetic Semiconductors by :
Download or read book Charge and Spin Transport in Dilute Magnetic Semiconductors written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This proposal to the DOE outlines a three-year plan of research in theoretical and computational condensed-matter physics, with the aim of developing a microscopic theory for charge and spin dynamics in disordered materials with magnetic impurities. Important representatives of this class of materials are the dilute magnetic semiconductors (DMS), which have attracted great attention as a promising basis for spintronics devices. There is an intense experimental effort underway to study the transport properties of ferromagnetic DMS such as (Ga, Mn)As, and a number of interesting features have emerged: negative magnetoresistance, anomalous Hall effect, non-Drude dynamical conductivity, and resistivity maxima at the Curie temperature. Available theories have been able to account for some of these features, but at present we are still far away from a systematic microscopic understanding of transport in DMS. We propose to address this challenge by developing a theory of charge and spin dynamics based on a combination of the memory-function formalism and time-dependent density functional theory. This approach will be capable of dealing with two important issues: (a) the strong degree of correlated disorder in DMS, close to the localization transition (which invalidates the usual relaxation-time approximation to the Boltzmann equation), (b) the essentially unknown role of dynamical many-body effects such as spin Coulomb drag. We will calculate static and dynamical conductivities in DMS as functions of magnetic order and carrier density, which will advance our understanding of recent transport and infrared absorption measurements. Furthermore, we will study collective plasmon excitations in DMS (3D, 2D and quantum wells), whose linewidths could constitute a new experimental probe of the correlation of disorder, many-body effects and charge and spin dynamics in these materials.
Book Synopsis Handbook of Spintronics by : Yongbing Xu
Download or read book Handbook of Spintronics written by Yongbing Xu and published by Springer. This book was released on 2015-10-14 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over two volumes and 1500 pages, the Handbook of Spintronics will cover all aspects of spintronics science and technology, including fundamental physics, materials properties and processing, established and emerging device technology and applications. Comprising 60 chapters from a large international team of leading researchers across academia and industry, the Handbook provides readers with an up-to-date and comprehensive review of this dynamic field of research. The opening chapters focus on the fundamental physical principles of spintronics in metals and semiconductors, including an introduction to spin quantum computing. Materials systems are then considered, with sections on metallic thin films and multilayers, magnetic tunnelling structures, hybrids, magnetic semiconductors and molecular spintronic materials. A separate section reviews the various characterisation methods appropriate to spintronics materials, including STM, spin-polarised photoemission, x-ray diffraction techniques and spin-polarised SEM. The third part of the Handbook contains chapters on the state of the art in device technology and applications, including spin valves, GMR and MTJ devices, MRAM technology, spin transistors and spin logic devices, spin torque devices, spin pumping and spin dynamics and other topics such as spin caloritronics. Each chapter considers the challenges faced by researchers in that area and contains some indications of the direction that future work in the field is likely to take. This reference work will be an essential and long-standing resource for the spintronics community.
Book Synopsis Magnetism and Spintronics in Carbon and Carbon Nanostructured Materials by : Sekhar Chandra Ray
Download or read book Magnetism and Spintronics in Carbon and Carbon Nanostructured Materials written by Sekhar Chandra Ray and published by Elsevier. This book was released on 2020-01-15 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetism and Spintronics in Carbon and Carbon Nanostructured Materials offers coverage of electronic structure, magnetic properties and their spin injection, and the transport properties of DLC, graphene, graphene oxide, carbon nanotubes, fullerenes, and their different composite materials. This book is a valuable resource for those doing research or working with carbon and carbon-related nanostructured materials for electronic and magnetic devices. Carbon-based nanomaterials are promising for spintronic applications because their weak spin-orbit (SO) coupling and hyperfine interaction in carbon atoms entail exceptionally long spin diffusion lengths (~100μm) in carbon nanotubes and graphene. The exceptional electronic and transport features of carbon nanomaterials could be exploited to build multifunctional spintronic devices. However, a large spin diffusion length comes at the price of small SO coupling, which limits the possibility of manipulating electrons via an external applied field. Assesses the relative utility of a variety of carbon-based nanomaterials for spintronics applications Analyzes the specific properties that make carbon and carbon nanostructured materials optimal for spintronics and magnetic applications Discusses the major challenges to using carbon nanostructured materials as magnetic agents on a mass scale
Book Synopsis Charge Transport, Spin Transport and Magneto-optics of Solid-state Topological Memory Devices by : Tonmoy Kumar Bhowmick
Download or read book Charge Transport, Spin Transport and Magneto-optics of Solid-state Topological Memory Devices written by Tonmoy Kumar Bhowmick and published by . This book was released on 2019 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological spin textures such as skyrmions are strong candidates for next-generation storage units and spintronic devices. Skyrmions formed on the surface of Topological Insulators (TIs) give rise to additional device functionalities. The skyrmion-TI heterostructure system shows quantized topological Hall effect (QTHE) without any external magnetic eld. This shows that the topological properties of the skyrmion spin texture can be imprinted on the Dirac electrons of the topological insulator. We also predict such a skyrmion-TI heterostructure will give rise to high gure-of-merit magneto-optic Kerr effects (MOKE). Optical dielectric tensor elements are calculated using a tight-binding model and the Kubo formula. We show that the Fermi level dependence of the MOKE signatures is distinct for the different magnetic textures. Based on this, a skyrmion optical memory device is proposed. Next, we investigate antiferromagnetic (AFM) skyrmion since it offers couple of advantages in terms of speed and stability compared to its ferromagnetic counterpart. We investigate how AFM skyrmions can be manipulated using temperature gradient to realize novel spintronic device. The effect of temperature gradients on AFM skyrmion dynamics is predicted using a numerical Landau Lifshitz Gilbert (LLG) model.
Book Synopsis Topological Quantum Numbers In Nonrelativistic Physics by : David Thouless
Download or read book Topological Quantum Numbers In Nonrelativistic Physics written by David Thouless and published by World Scientific. This book was released on 1998-03-12 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological quantum numbers are distinguished from quantum numbers based on symmetry because they are insensitive to the imperfections of the systems in which they are observed. They have become very important in precision measurements in recent years, and provide the best measurements of voltage and electrical resistance. This book describes the theory of such quantum numbers, starting with Dirac's argument for the quantization of electric charge, and continuing with discussions on the helium superfluids, flux quantization and the Josephson effect in superconductors, the quantum Hall effect, solids and liquid crystals, and topological phase transitions. The accompanying reprints include some of the classic experimental and theoretical papers in this area.Physicists — both experimental and theoretical — who are interested in the topic will find this book an invaluable reference.
Book Synopsis Magnetic Multilayers by : Lawrence H Bennett
Download or read book Magnetic Multilayers written by Lawrence H Bennett and published by World Scientific. This book was released on 1994-12-16 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on an increasingly important area of materials science and technology, namely, the fabrication and properties of artificial materials where slabs of magnetized materials are sandwiched between slabs of nonmagnetized materials. It includes reviews by experts on the theory and descriptions of the various experimental techniques such as those using nuclear or electron spin probes, as well as optical, X-ray or neutron probes. It also reviews potential applications such as the giant magnetoresistance, and one specialized preparation technique, the electrodeposition. The various chapters are tutorial in nature, making the subject accessible to nonspecialists, as well as useful to researchers in the field.
Book Synopsis Topology in Magnetism by : Jiadong Zang
Download or read book Topology in Magnetism written by Jiadong Zang and published by Springer. This book was released on 2018-09-24 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents both experimental and theoretical aspects of topology in magnetism. It first discusses how the topology in real space is relevant for a variety of magnetic spin structures, including domain walls, vortices, skyrmions, and dynamic excitations, and then focuses on the phenomena that are driven by distinct topology in reciprocal momentum space, such as anomalous and spin Hall effects, topological insulators, and Weyl semimetals. Lastly, it examines how topology influences dynamic phenomena and excitations (such as spin waves, magnons, localized dynamic solitons, and Majorana fermions). The book also shows how these developments promise to lead the transformative revolution of information technology.
Book Synopsis Nanomagnetism and Spintronics by : Farzad Nasirpouri
Download or read book Nanomagnetism and Spintronics written by Farzad Nasirpouri and published by World Scientific. This book was released on 2011 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomagnetism and spintronics are two close subfields of nanoscience, explaining the effect of substantial magnetic properties of matter when the materials fabrication is realized at a comparable length size. Nanomagnetism deals with the magnetic phenomena specific to the structures having dimensions in the submicron range. The fact that the electronic transport properties of materials are dependent on the magnetic properties' artificial nanostructures, i.e., giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR), has revolutionized spintronics science and technology. This book explains the concepts of nanomagnetism and spintronics by viewing the most recent research works from internationally distinguished research groups. Placing special emphasis on crucial fundamental and technical aspects of nanomagnetism and spintronics, it serves as a one-stop reference for universities offering postgraduate programs in nanotechnology or related disciplines. This unique book deals with all three stages required for conducting research in nanomagnetism and spintronics including fabrication, characterization and applications of nanomagnetic and spintronics materials, providing general concepts and an insightful overview of this subject for research students and scientists from different backgrounds investigating the multidisciplinary area of nanotechnology.
Book Synopsis Organic Nanostructures: Science and Applications by : V.M. Agranovich
Download or read book Organic Nanostructures: Science and Applications written by V.M. Agranovich and published by IOS Press. This book was released on 2002-11-19 with total page 653 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Enrico Fermi School, the first one dedicated to advanced organic materials, the main research results and open problems in science and technology of organic nanostructures have been discussed; in particular, growth techniques, electronic and optical properties, device applications. The necessary background material has been covered and interdisciplinary aspects have been emphasized with the aim of a unified approach to the basic physical phenomena bridging the gap between standard graduate courses and the state of the art in the field. The lecturers have provided authoritative and comprehensive tutorial reviews of the main issues involved in the science and technology of organic materials and their nanostructures. In particular, the following topics have been specifically addressed: charge carrier mobility and transport properties, electrical conductivity of conjugated polymers, charge transfer states in organics, photorefractivity in organics, energy transfer processes in organics, photophysics and fast spectroscopy, technology of polymer electronics and light emitting devices.
