Magnetic Excitation-Induced Spin Current (original) (raw)
Perspectives of electrically generated spin currents in ferromagnetic materials
Physics Letters A
Spin-orbit coupling enables charge currents to give rise to spin currents and vice versa, which has applications in non-volatile magnetic memories, miniature microwave oscillators, thermoelectric converters and Terahertz devices. In the past two decades, a considerable amount of research has focused on electrical spin current generation in different types of nonmagnetic materials. However, electrical spin current generation in ferromagnetic materials has only recently been actively investigated. Due to the additional symmetry breaking by the magnetization, ferromagnetic materials generate spin currents with different orientations of spin direction from those observed in nonmagnetic materials. Studies centered on ferromagnets where spin-orbit coupling plays an important role in transport open new possibilities to generate and detect spin currents. We summarize recent developments on this subject and discuss unanswered questions in this emerging field. paul.haney@nist.gov xin.fan@du.edu * These two authors contributed equally to the manuscript.
Magnetic interactions and spin transport
2003
This book originated as a series of lectures that were given as part of a Summer School on Spintronics in the end of August, 1998 at Lake Tahoe, Nevada. It has taken some time to get these lectures in a form suitable for this book and so the process has been an iterative one to provide current information on the topics that are covered. There are some topics that have developed in the intervening years and we have tried to at least alert the readers to them in the Introduction where a rather complete set of references is provided to the current state of the art. The field of magnetism, once thought to be dead or dying, has seen a remarkable rebirth in the last decade and promises to get even more important as we enter the new millennium. This rebirth is due to some very new insight into how the spin degree of freedom of both electrons and nucleons can play a role in a new type of electronics that utilizes the spin in addition to or in place of the charge. For this new field to mature and prosper, it is important that students and postdoctoral fellows have access to the appropriate literature that can give them a sound basis in the fundamentals of this new field and I hope that this book is a very good start in this direction. The Chapter 1 covers the physical concepts related to the magnetic and electrical properties of transition metal oxides. These materials are important for some of the existing as well as future applications of spintronics. Chapter 2 provides a fundamental description of the origins of magnetocrystalline anisotropy resulting from spin-orbit interactions and magnetism. It also deals with the magneto-optic properties of materials such as the Kerr and Faraday effects which are important tools for understanding magnetic properties of materials. Chapter 3 addresses many of the theoretical aspects of spin transport, mostly in metallic systems. Chapter 4 provides an overview of experimental results on spin transport and covers such topics as GMR and spin dependent tunneling. Chapter 5 describes in detail methods for quantitative measurements of the magnetization of materials. This chapter provides a detailed description of magnetic units and their connection to the measurements of magnetic properties. Instruments described in this chapter are the vibrating sample magnetometer, the SQUID magnetometer, Mossbauer spectrometers and NMR spectrometers. Chapter 6 reviews experimental techniques for looking at surface magnetism and involves Kerr microscopy, scanning electron microscopy with polarization analysis, magnetic force microscopy, x-ray dichroism, etc. v vi PREFACE Chapter 7 discusses the origins of magnetic noise that in some sense is the limiting characteristic for many state of the art magnetic devices including magnetic disk storage. Chapter 8 describes the methods for preparing thin films of magnetic materials that include molecular beam epitaxy (MBE), sputtering and pulsed laser deposition. Chapter 9 is a description of magnetic sensors, Chapter 10 is a detailed description of magneto-resistive memories and Chapter 11 is a description of hybrid magnetic devices. I hope that this book will provide an important introduction to the very exciting and potentially revolutionary field of spin electronics.
Theory of spin transfer phenomena in magnetic metals and semiconductors
Solid State Communications, 2006
We propose a general theory of the spin-transfer effects that occur when current flows through inhomogeneous magnetic systems. Our theory does not rest on an appeal to conservation of total spin, can assess whether or not current-induced magnetization precession and switching in a particular geometry will occur coherently, and can estimate the efficacy of spin-transfer when spin-orbit interactions are present. We illustrate our theory by applying it to a toy-model twodimensional-electron-gas ferromagnet with Rashba spin-orbit interactions. q
arXiv: Mesoscale and Nanoscale Physics, 2020
Motivated by the rising importance of understanding various competing mechanisms to current-induced torque in complex magnets, we develop a unified theory of current-induced spin-orbital coupled dynamics, which tracks the transfer of angular momentum between different degrees of freedom in solids: spin and orbital of the electron, lattice, and local magnetic moment. From the continuity equations for the spin and orbital angular momenta, we derive equations of motion that relate spin and orbital current fluxes and torques describing the transfer of angular momentum between different degrees of freedom, in a steady state under an external electric field. We apply our formalism to two different magnetic bilayers, Fe/W(110) and Ni/W(110), where the orbital and spin Hall effects in W have opposite sign and the resulting spin- and orbital-mediated torques can compete with each other. We find that while the torque arising from the spin Hall effect of W is the dominant mechanism of the curr...
Magnetic Properties: From Traditional to Spintronic
Springer Handbook of Electronic and Photonic Materials, 2017
This chapter reviews basic concepts used in the traditional macroscopic magnetism in order to understand current and future developments of submicronic spin-based electronics where interplay of electronic and magnetic properties is crucial. Traditional magnetism is based on macroscopic observation and physical quantities are deduced from classical electromagnetism. Physical interpretations are usually made with reference to atomic magnetism where localized magnetic moments and atomic physics prevail, despite the fact that standard ferromagnetic materials such as Fe, Co, and Ni are not localized-type magnets (they have extended s and localized d electronic states). While this picture might be enough to understand some aspects of traditional storage and electromechanics, it is no longer sufficient for the description of condensed matter systems with smaller length scales progressing toward the nanometer range. The precise nature of magnetism (localized, free, or itinerant like Fe, Co, and Ni transition metals) with simultaneous presence of charge and spin of carriers should be considered. In addition, when we deal with thin films or multilayers as in conventional electronics or with reduced dimensionality objects such as wires, pillars, dots, or grains, magnetic properties are expected to be different from three-dimensional conventional bulk systems.
Optical spin transfer in ferromagnetic semiconductors
Arxiv preprint cond-mat/0304492, 2003
Abstract: Circularly polarized laser pulses that excite electron-hole pairs across the band gap of (III, Mn) V ferromagnetic semiconductors can be used to manipulate and to study collective magnetization dynamics. The initial spin orientation of a photocarrier in a (III, V) semiconductors is determined by the polarization state of the laser. We show that the photocarrier spin can be irreversibly transferred to the collective magnetization, whose dynamics can consequently be flexibly controlled by suitably chosen laser pulses. As ...
Spin-Dependent Currents in Magnet/Normal Metal Based Magnetic Nanostructures
American Journal of Nano Research and Applications, 2017
The spin transport through and near interfaces have been studied in magnet/normal metal based multilayer magnetic nanostructures in magneto-static and magneto-dynamic cases. Its features and accompanying effects, such as the magnetoresistance or the magnetic precession induced spin pumping and spin accumulation in adjacent normal metal are determined by the spin-dependent scattering on the interface. These effects are governed by the entire spin-coherent region that is limited in size by spin-flip relaxation processes and can be controlled by the spin-polarized current of different origin including the spin Hall effect. Conditions of realization of the mentioned spin currents in the multilayer magnetic nanostructures are studied.
Spin Transport and Dynamics in Multilayer Magnetic Nanostructures
American Journal of Nano Research and Applications
The interconnection between the spin current and spin dynamics via the spin-dependent scattering and an accompanying by spin torque effect in ferromagnetic/normal metal based magnetic multilayer nanostructures is studied including a high fast out-of-equilibrium spin dynamics. Features of the spin transport through interfaces and its impact on spin dynamics are described on the base of the scattering matrix formalism for spin flows. The dependence of the spin torque effect on conductance character of the normal metal layers is considered. The exchange processes between the itinerant s and the localized d electrons are described by kinetic rate equations for electron-magnon spin-flop scattering. It is shown that the magnon distribution function remains nonthermalized on the relevant time scales of the demagnetization process, and the relaxation of the out-of-equilibrium spin accumulation among itinerant electrons provides the principal channel for dissipation of spin angular momentum from the combined electronic system.