Download or read book Quantum Spin Transport and Collective Magnetic Dynamics in Heterostructures written by Scott Andrew Bender and published by . This book was released on 2014 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis advances the theory of quantum and semiclassical transport in magnetic heterostructures. In the solid state, angular momentum can be carried by individual electrons and collective modes. The flow of angular momentum (a spin current), central to the operation of spintronic devices, is generated by the application of electric and magnetic fields and temperature gradients. In what follows, we explore the physics of such nonequilibrium spin currents in magnetic structures, involving an interplay of charge and magnetic dynamics and thermoelectric effects. Chapter 1 provides an introduction to the transport of spin in magnets, carried by electrons and collective excitations of the magnetic order. Chapters 2-6 study the role of thermal fluctuations in transport and magnetic dynamics. In Chapter 2, we describe how incoherent thermal fluctuations of the spin density (magnons), which open inelastic scattering channels, contribute to spin and energy transport between a normal metal and a magnet. Such (temperature-dependent) transport may arise from a thermal gradient applied across the metal/magnet interface or a spin accumulation inside the normal metal and may alter or even drive magnetic dynamics. Chapter 3, is dedicated to the realization of Bose-Einstein condensed magnons (previously observed by microwave pumping) in a normal metal/insulating ferromagnet heterostructure. As is described in Chapter 2, the combination of a temperature gradient and normal metal spin accumulation can drive spin into the insulating ferromagnet, accumulating as magnons; upon reaching a critical density, the magnons, which are bosonic, spontaneously form a quasi-equilibrium condensate. Chapter 4 focuses on thermally driven spin-torques in electrically insulating structures, wherein direct electric control of magnetic dynamics is prohibited. In contrast to the interfacial transport described in Chapter 2, where a spin accumulation is to necessary to observe magnetic dynamics, here we demonstrate how spin-torques can arise from a pure thermal gradient in a heterostructure. These spin-torques can be measured by ferromagnetic resonance and can, under a sufficiently strong bias, actuate magnetic switching. Chapter 5 concerns charge transport in a single-electron transistor, consisting of a magnetic quantum dot in contact with magnetic and normal metal leads. Microwave-driven precession by the dot induces a pumped electric current, which can be enhanced and made highly nonlinear by electron interactions (Coulomb blockade). The dependence of the resulting electrical response on the power and spectrum of microwave irradiation may be utilized to develop nanoscale microwave detectors analogous to single-electron transistor-based electrostatic sensors and nanoelectromechanical devices. In Chapter 6 we study bilayers, composed of a nonmagnetic conducting and a magnetic layer. We develop a general phenomenology for the magnetic and charge dynamics, which are coupled by spin-orbit interactions. In contrast to Chapters 2-4, we focus on the long-wavelength magnetic dynamics, which is subject to current-induced torques and produces fictitious electromotive forces that drive charge dynamics.}

Download or read book Spin Transport and Dynamics in Magnetic Heterostructures written by Jack T. Brangham and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Spintronics research over the past two decades has focused on developing an understanding of spin transport in materials currently used in the semiconductor industry for potential spin-based applications. Recently, a surge of interest in spin transport in antiferromagnetic materials and spin interactions in novel materials have led to many promising discoveries. The work in this dissertation explores discrepancies in past discoveries, provides evidence to support recent theories on antiferromagnetic (AFM) spin transport, and develops the capabilities to further explore spin physics in novel states of matter. This dissertation focuses on four primary topics. First, a thickness dependence of the spin Hall angle in Au is discussed as a potential explanation for a large variance in the previously reported values. Second, evidence supporting a highly efficient mode of spin transport mediated by AFM fluctuations is found in the temperature dependence of the spin pumping signal in Pt/NiO/Y3Fe5O12 trilayers. Third, a new low damping metallic ferromagnet is developed and characterized as a potential platform for future spintronic research. Finally, a molecular beam epitaxy system is established with the capabilities to prepare topologically insulating materials that are predicted to host many novel phenomena.

Download or read book Spin Dynamics in Two Dimensional Quantum Materials written by Marc Vila Tusell and published by Springer Nature. This book was released on 2021-11-10 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on the exploration of nontrivial spin dynamics in graphene-based devices and topological materials, using realistic theoretical models and state-of-the-art quantum transport methodologies. The main outcomes of this work are: (i) the analysis of the crossover from diffusive to ballistic spin transport regimes in ultraclean graphene nonlocal devices, and (ii) investigation of spin transport and spin dynamics phenomena (such as the (quantum) spin Hall effect) in novel topological materials, such as monolayer Weyl semimetals WeTe2 and MoTe2. Indeed, the ballistic spin transport results are key for further interpretation of ultraclean spintronic devices, and will enable extracting precise values of spin diffusion lengths in diffusive transport and guide experiments in the (quasi)ballistic regime. Furthermore, the thesis provides an in-depth theoretical interpretation of puzzling huge measured efficiencies of the spin Hall effect in MoTe2, as well as a prediction of a novel canted quantum spin Hall effect in WTe2 with spins pointing in the yz plane.

Download or read book Handbook of Spin Transport and Magnetism written by Evgeny Y. Tsymbal and published by CRC Press. This book was released on 2011-08-25 with total page 809 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past several decades, the research on spin transport and magnetism has led to remarkable scientific and technological breakthroughs, including Albert Fert and Peter Grünberg’s Nobel Prize-winning discovery of giant magnetoresistance (GMR) in magnetic metallic multilayers. Handbook of Spin Transport and Magnetism provides a comprehensive, balanced account of the state of the art in the field known as spin electronics or spintronics. It reveals how key phenomena first discovered in one class of materials, such as spin injection in metals, have been revisited decades later in other materials systems, including silicon, organic semiconductors, carbon nanotubes, graphene, and carefully engineered nanostructures. The first section of the book offers a historical and personal perspective of the field written by Nobel Prize laureate Albert Fert. The second section addresses physical phenomena, such as GMR, in hybrid structures of ferromagnetic and normal metals. The third section discusses recent developments in spin-dependent tunneling, including magnetic tunnel junctions with ferroelectric barriers. In the fourth section, the contributors look at how to control spin and magnetism in semiconductors. In the fifth section, they examine phenomena typically found in nanostructures made from metals, superconductors, molecular magnets, carbon nanotubes, quantum dots, and graphene. The final section covers novel spin-based applications, including advanced magnetic sensors, nonvolatile magnetoresistive random access memory, and semiconductor spin-lasers. The techniques and materials of spintronics have rapidly evolved in recent years, leading to vast improvements in hard drive storage and magnetic sensing. With extensive cross-references between chapters, this seminal handbook provides a complete guide to spin transport and magnetism across various classes of materials and structures.

Download or read book Spin Dynamics and Transport in Magnetic Heterostructures written by Tobias Schneider and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Spin Pumping and Spin Transport in Magnetic Heterostructures written by Eric Montoya and published by . This book was released on 2016 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: High quality, ultrathin magnetic films were prepared by means of molecular beam epitaxy (MBE). Magnetization dynamics and anisotropies were studied by means of ferromagnetic resonance (FMR) in GaAs.

Download or read book Spin Dynamics and Damping in Ferromagnetic Thin Films and Nanostructures written by Anjan Barman and published by Springer. This book was released on 2017-12-27 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the latest developments in the field of spin dynamics and magnetic damping. It discusses the various ways to tune damping, specifically, dynamic and static control in a ferromagnetic layer/heavy metal layer. In addition, it addresses all optical detection techniques for the investigation of modulation of damping, for example, the time-resolved magneto-optical Kerr effect technique.

Download or read book Spin Dynamics in Confined Magnetic Structures I written by Burkard Hillebrands and published by Springer Science & Business Media. This book was released on 2001-11-06 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introductory chapters help newcomers to understand the basic concepts, and the more advanced chapters give the current state of the art for most spin dynamic issues in the milliseconds to femtoseconds range. Emphasis is placed on both the discussion of the experimental techniques and on the theoretical work. The comprehensive presentation of these developments makes this volume very timely and valuable for every researcher working in the field of magnetism.

Download or read book Spin Transport in Rare Earth Magnetic Heterostructures written by Aidan Thomas Hindmarch and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oxford Handbook of Nanoscience and Technology written by A.V. Narlikar and published by Oxford University Press. This book was released on 2010-02-11 with total page 957 pages. Available in PDF, EPUB and Kindle. Book excerpt: These three volumes are intended to shape the field of nanoscience and technology and will serve as an essential point of reference for cutting-edge research in the field.

Download or read book Spin Dynamics in Confined Magnetic Structures III written by Burkard Hillebrands and published by Springer. This book was released on 2014-10-20 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The third volume of this book addresses central aspects of spin-dynamic phenomena on a tutorial level. This volume concentrates on new experimental techniques such as ferromagnetic-resonance-force microscopy and two-photon photoemission. There is a chapter devoted to the hot subject of spin-transfer torque. The comprehensive presentation makes this a timely and valuable resource for every researcher working in the field of magnetism.

Download or read book Spin Transport and Dynamics in Antiferromagnetic Metals and Magnetic Insulators written by A. C. Swaving and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spin Transport and Magnetization Dynamics in Various Magnetic Systems written by Shulei Zhang and published by . This book was released on 2014 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: The general theme of the thesis is the interplay between magnetization dynamics and spin transport. The main presentation is divided into three parts. The first part is devoted to deepening our understanding on magnetic damping of ferromagnetic metals, which is one of the long-standing issues in conventional spintronics that has not been completely understood. For a nonuniformly-magnetized ferromagnetic metal, we find that the damping is nonlocal and is enhanced as compared to that in the uniform case. It is therefore necessary to generalize the conventional Landau-Lifshitz-Gilbert equation to include the additional damping. In a different vein, the decay mechanism of the uniform precession mode has been investigated. We point out the important role of spin-conserving electron-magnon interaction in the relaxation process by quantitatively examining its contribution to the ferromagnetic resonance linewidth. In the second part, a transport theory is developed for magnons which, in addition to conduction electrons, can also carry and propagate spin angular momentum via the magnon current. We demonstrate that the mutual conversion of magnon current and spin current may take place at magnetic interfaces. We also predict a novel magnon-mediated electric drag effect in a metal/magnetic-insulator/metal trilayer structure. This study may pave the way to the new area of insulator-based spintronics. In the third part of thesis, particular attention is paid to the influence the spin orbit coupling on both charge and spin transport. We theoretically investigate magnetotransport anisotropy and the conversion relations of spin and charge currents in various magnetic systems, and apply our results to interpret recent experiments.

Download or read book Magnetization and Spin Dynamics in Complex Oxide Heterostructures written by Jacob John Wisser and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Information processing via pure spin currents requires new materials for efficient generation and transport of pure spin currents. One promising class of materials for this application is the complex oxides, which offer a wide variety of properties including ferromagnetic insulating behavior, superconductivity, and antiferromagnetism. I will explore each of these properties for spintronic applications in this thesis. I have developed a series of low damping ferromagnetic insulators in thin film form as a medium for low loss spin wave propagation. I optimized the thickness and composition of MgAl(2-x)FexO4 (MAFO) thin films for low Gilbert damping measured via ferromagnetic resonance (FMR). In an effort to understand spin current transport across interfaces and quantify spin transport parameters, I then interfaced MAFO thin films with Cu and Pt capping layers and compared this system to another spinel ferrite used for spin current generation, Ni0.65Zn0.35Al0.8Fe1.2O4 (NZAFO). I found the interfaces in these heterostructures played a dominant role in the FMR properties, so much so that quantifying spin current transport parameters became difficult. To eliminate the polycrystalline interface and improve transport across the interface, I then interfaced MAFO with another spinel oxide, CrCo2O4. Even in this isostructural bilayer, I found the interface dominated the FMR properties and led to damping increases on the order of that observed in MAFO/Pt bilayers. These results highlighted the importance of considering the interface in spin pumping heterostructures when analyzing spin transport parameters. In the next part of the thesis, I investigate the interaction between superconductivity and spin current transport in isostructural La0.67Sr0.33MnO3 (LSMO)/ YBa2Cu3O7 (YBCO) bilayers. Superconductors have the potential to have extremely long spin diffusion lengths, but these parameters have yet to be measured in anisotropic d-wave superconductors such as YBCO. Using a custom FMR insert for our cryostat, I probed spin current transport across the superconducting transition. However, I again found the interface between the LSMO and YBCO layers played an important role. The diffuse layer between the two led to complex behavior across the superconducting transition that was due to other sources of damping increase than spin pumping, such as two-magnon scattering (TMS) processes. To alleviate this issue, I also studied YBCO / Ni20Fe80 bilayers, which were known to have a lower contribution from TMS. While I did find some evidence for the coexistence of spin pumping and superconductivity in these bilayers, the polycrystalline interface appeared to play an important role in the spin dynamics. As before these results underscored the importance of the spin source/sink interface when analyzing spin pumping heterostructures. In the final part of the thesis, I developed antiferromagnetic materials for high-frequency spintronic applications. Antiferromagnetic materials have much higher characteristic frequencies, pushing the timescale for dynamics into the THz regime. I began with fabricating free-standing NiO membranes for ultrafast electron diffraction (UED) experiments. I used a new technique to fabricate oxide membranes, and maintained high crystalline quality and orientation while transferring thin films onto Si TEM grids for the UED experiment. I will then present analysis of the Debye-Waller effect in (001) NiO membranes. I then characterized the structure and spin-Hall magnetoresistance in Cr2O3 thin films on various orientations of Al2O3 substrates. Cr2O3 has been shown to undergo resonance at high frequencies in bulk, but there has yet to be an analogous study for thin films. I measured a crossover between ferromagnetic behavior dominated by uncompensated moments at the surface and bulk antiferromagnetic behavior in the magneotransport. These results combined demonstrated the viability of the NiO and Cr2O3 systems for future experiments for high-frequency spintronic applications.

Download or read book Semiclassical Theory of Spin Transport in Metallic and Semiconductor Heterostructures written by Yunong Qi and published by . This book was released on 2003 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, transport properties of magnetic nanostructures have been one of the most active research areas of Condensed Matter Physics. Many emerging scientific issues are not satisfactorily answered. This Thesis will be focused on one of the most important theoretical problems in magnetic nanostructures; namely, it aims at a better understanding of magnetotransport phenomena. Two most common scattering mechanisms, diffusive scattering in the bulk of the layers (or particles) and ballistic scattering at the interface (or boundaries) are believed to be the main sources of magnetoresistance (or resistance). Previously, one usually takes the bulk and interface scattering either ballistically or diffusively, but not both. In a realistic experimental structure, both scatterings exist and they are equally important. A unified theory of spin transport was established by using semiclassical Boltzmann equation approach in this Thesis. This work significantly generalizes previous scattering theories and can be broadly used to understand the magnetotransport properties of a variety of magnetic nanostructures. With this formalism, the interface and bulk scatterings can be successfully treated on equal footing. The conductance and magnetoresistance of a pinhole structure, then, can be calculated. It is found that both conductance and magnetoresistance can be optimized to desired values for magnetic recording application. To extend our model to semiconductor heterostructures, a more generalized, theoretical model has been developed in the study of non-zero magnetic and electric fields effects on spin transport properties. It is found that the spin-diffusion equation for non-equilibrium spin density and spin current density involves a number of new relevant length scales that explicitly depend on the electric and magnetic fields. The set of macroscopic equations can be used to address a very broad range of spin transport problems from magnetic, metallic multilayers to semiconductor heterostructures. The subject of spin transport we have completed is not only fundamentally interesting from the viewpoint of theoretical and material physics, but also greatly important for the development of emerging technology such as magnetic random access memory (MRAM) (which is a novel, non-volatile device and potential use for storing information in the computer), transistor, and possibly quantum computers.

Download or read book Three Dimensional Magnonics written by Gianluca Gubbiotti and published by CRC Press. This book was released on 2019-07-10 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnonics, a research field that uses spin waves, collective excitations of ordered magnetic materials, or magnons (their quanta) as a tool for signal processing, communication, and computation, has rapidly grown during the past decade because of the low-energy consumption and potential compatibility with next-generation circuits beyond CMOS electronics. The interest in 3D magnonic nanostructures follows the latest trend in conventional electronics based on expansion from 2D planar to 3D vertically integrated structures. To remain on the same technological level, a similar expansion should be realized in magnonics. Following this trend, this book provides an overview of recent developments in the exploitation of the third dimension in magnonics, with special focus on the propagation of spin waves in layered magnonic crystals, spin textures, curved surfaces, 3D nano-objects, and cavity magnonics.