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Characterization Of Spin Transfer Torque And Magnetization Manipulation In Magnetic Nanostructures
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Book Synopsis Characterization of Spin Transfer Torque and Magnetization Manipulation in Magnetic Nanostructures by : Chen Wang
Download or read book Characterization of Spin Transfer Torque and Magnetization Manipulation in Magnetic Nanostructures written by Chen Wang and published by . This book was released on 2012 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes a number of research projects with the common theme of manipulating the magnetization of a nanoscale magnet through electrical means, and the major part is devoted to exploring the effect of spin angular momentum transfer from a spin-polarized current to a nanomagnet, which we call spin transfer torque. Spin transfer torque is a promising new mechanism to "write" magnetic storage elements in magnetic random access memory (MRAM) devices with magnesium oxide (MgO)-based magnetic tunnel junction (MTJ) architecture. The first part of our work aims at a quantitative measurement of the spin transfer torque exerted on one of the ferromagnetic electrodes in exactly this type of tunneling structures used for MRAM applications. We use a technique called spin-transfer-driven ferromagnetic resonance (ST-FMR), where we apply a microwave-frequency oscillating current to resonantly excite magnetic precession, and we describe two complementary methods to detect this precession. We resolve previous controversies over the bias dependence of spin transfer torque, and present the first quantitative measurement of spin transfer torque in MgO-based MTJs in full bias range. We also analyze and test the potential to use the ST-FMR technique for microwave detection and microwave amplification. In the second part of the our work, we fabricate ferromagnetic nanoparticles made of CoFeB or Co embedded in the MgO tunnel barrier of a typical magnetic tunnel junction device, and study the spin transfer torque exerted on these nanoparticles 2-3 nm in size. We present the first evidence of spin transfer torque in magnetic nanoparticles insulated from electrodes by mapping out the switching phase diagram of a single nanoparticle. We also study ferromagnetic resonance of a small number of nanoparticles induced by spin transfer torque, with the goal of approaching single electron tunneling regime. The last part of our work explores a dramatically different way to manipulate magnetization electrically. We couple a ferromagnet to a multiferroic material, bismuth ferrite (BiFeO3), by exchange bias interaction, and try to manipulate the ferromagnet by ferroelectric switching of the BiFeO3.
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 Characterization of Magnetic Dynamics Excited by Spin Transfer Torque in a Nanomagnet by : Yongtao Cui
Download or read book Characterization of Magnetic Dynamics Excited by Spin Transfer Torque in a Nanomagnet written by Yongtao Cui and published by . This book was released on 2012 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents our investigation of the effects of spin transfer torque on a nanoscale ferromagnet. Spin transfer torque is generated by the transfer of angular momentum from spin polarized electrons to a ferromagnet. This torque provides an efficient means to manipulate the dynamic motion of the magnetization of a nanomagnet, and can be strong enough to induce magnetization reversal or steady-state precession. We have developed new techniques to characterize such dynamics induced by spin transfer torque. In the first study, we perform an experiment demonstrating that spin transfer from a microwave current pulse can produce a resonant excitation of a nanomagnet and improve switching characteristics in combination with a square current pulse. With the assistance of a microwave-frequency pulse, the switching time is reduced and achieves a narrower distribution than when driven by a square current pulse alone, and this can permit significant reductions in the integrated power required for switching. In the second study, we develop a single-shot electrical technique to capture the magnetic dynamics during the spin torque switching of a magnetic tunnel junction in real time. With substantially improved sensitivity compared to previous experiments, we directly resolve the resistance oscillations associated with magnetic dynamics, yielding detailed views of switching modes and variations between events. This also enables us to analyze the coherence times and non-equilibrium spectra of the magnetic dynamics under the effects of thermal fluctuations. In the last study, we use X-ray microscopy to image the magnetic normal modes which serve as the basis states for the magnetic dynamics. By applying a microwave current at the normal mode frequency, we selectively excite a particular normal mode and perform time resolved X-ray microscopy measurement to image its spatial structure. We observe different degrees of spatial non-uniformity for two mode branches we imaged. The branch with higher frequency is more spatially uniform than the other. At low magnetic fields where the two modes are close in frequency and excited at the same time, the more non-uniform mode dominates the overall behavior of the dynamics.
Book Synopsis Nanomagnetism and Spintronics by : Teruya Shinjo
Download or read book Nanomagnetism and Spintronics written by Teruya Shinjo and published by Elsevier. This book was released on 2013-10-07 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: The concise and accessible chapters of Nanomagnetism and Spintronics, Second Edition, cover the most recent research in areas of spin-current generation, spin-calorimetric effect, voltage effects on magnetic properties, spin-injection phenomena, giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR). Spintronics is a cutting-edge area in the field of magnetism that studies the interplay of magnetism and transport phenomena, demonstrating how electrons not only have charge but also spin. This second edition provides the background to understand this novel physical phenomenon and focuses on the most recent developments and research relating to spintronics. This exciting new edition is an essential resource for graduate students, researchers, and professionals in industry who want to understand the concepts of spintronics, and keep up with recent research, all in one volume. Provides a concise, thorough evaluation of current research Surveys the important findings up to 2012 Examines the future of devices and the importance of spin current
Book Synopsis Characterization of Magnetic Tunnel Junctions for Spin Transfer Torque Magnetic Random Access Memory by : Joshua Dill
Download or read book Characterization of Magnetic Tunnel Junctions for Spin Transfer Torque Magnetic Random Access Memory written by Joshua Dill and published by . This book was released on 2014 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis details two experimental methods for quantifying magnetic tunnel junction behavior, namely write error rates and field modulated spin-torque ferromagnetic resonance. The former examines how reliably an applied spin-transfer torque can excite magnetization dynamics that lead to a reversal of magnetization direction while the latter studies steady state dynamics provided by an oscillating spin-transfer torque. These characterization techniques reveal write error rate behavior for a particular composition magnetic tunnel junction that qualitatively deviates from theoretical predictions. Possible origins of this phenomenon are also investigated with the field modulated spin-torque ferromagnetic resonance technique. By understanding the dynamics of magnetic moments predicted by theory, one can experimentally confirm or disprove these theories in order to accurately model and predict tunnel junction behavior. By having a better model for what factors are important in magnetization dynamics, one can optimize these factors in terms of improving magnetic tunnel junctions for their use as computer memory.
Book Synopsis Spin-transfer Torque in Magnetic Nanostructures by : Jiang Xiao
Download or read book Spin-transfer Torque in Magnetic Nanostructures written by Jiang Xiao and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis consists of three distinct components: (1) a test of Slocnzewski's theory of spin-transfer torque using the Boltzmann equation, (2) a comparison of macrospin models of spin-transfer dynamics in spin valves with experimental data, and (3) a study of spin-transfer torque in continuously variable magnetization. Slonczewski developed a simple circuit theory for spin-transfer torque in spin valves with thin spacer layer. We developed a numerical method to calculate the spin-transfer torque in a spin valve using Boltzmann equation. In almost all realistic cases, the circuit theory predictions agree well with the Boltzmann equation results. To gain a better understanding of experimental results for spin valve systems, current-induced magnetization dynamics for a spin valve are studied using a single-domain approximation and a generalized Landau-Lifshitz-Gilbert equation. Many features of the experiment were reproduced by the simulations. However, there are two significant discrepancies: the current dependence of the magnetization precession frequency, and the presence and/or absence of a microwave quiet magnetic phase with a distinct magnetoresistance signature. Spin-transfer effects in systems with continuously varying magnetization also have attracted much attention. One key question is under what condition is the spin current adiabatic, i.e., aligned to the local magnetization. Both quantum and semi-classical calculations of the spin current and spin-transfer torque are done in a free-electron Stoner model. The calculation shows that, in the adiabatic limit, the spin current aligns to the local magnetization while the spin density does not. The reason is found in an effective field produced by the gradient of the magnetization in the wall. Non-adiabatic effects arise for short domain walls, but their magnitude decreases exponentially as the wall width increases.
Book Synopsis Handbook of Nanomagnetism by : Rosa A. Lukaszew
Download or read book Handbook of Nanomagnetism written by Rosa A. Lukaszew and published by CRC Press. This book was released on 2015-10-06 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique handbook compiles and details cutting-edge research in nanomagnetism and its applications in spintronics, magnetoplasmonics, and nonlinear magneto-optics. Fundamental aspects of magnetism relevant to nanodevices and new spin-transfer torque random-access memory (STT-RAM), current-induced domain wall motion memory, and spin torque oscill
Download or read book Nanomagnetism written by Claude Fermon and published by John Wiley & Sons. This book was released on 2017-03-17 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first book to focus on the applications of nanomagnetism presents those already realized while also suggesting bold ideas for further breakthroughs. The first part is devoted to the concept of spin electronics and its use for data storage and magnetic sensing, while the second part concentrates on magnetic nanoparticles and their use in industrial environment, biological and medical applications. The third, more prospective part goes on to describe emerging applications related to spin current creation and manipulation, dynamics, spin waves and binary logic based on nano-scale magnetism. With its unique choice of topics and authors, this will appeal to academic as well as corporate researchers in a wide range of disciplines from physics via materials science to engineering, chemistry and life science.
Book Synopsis Magnetic Nanostructures by : Hartmut Zabel
Download or read book Magnetic Nanostructures written by Hartmut Zabel and published by Springer. This book was released on 2012-09-15 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.
Book Synopsis Functional Materials and Electronics by : Jiabao Yi
Download or read book Functional Materials and Electronics written by Jiabao Yi and published by CRC Press. This book was released on 2018-05-11 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: This informative book focuses on newly developed functional materials and their applications for electronic and spintronic devices. Electronic devices have become a part of our daily modern life, involving mobile phones, data storage, computers, and satellites, and there is relentless growth in microelectronics. This volume covers the topics of oxide materials for electronics devices, new materials, and new properties, especially in newly developed research areas, such as oxide magnetic semiconductors and two-dimensional electron gas. Key features: Emphasizes functional materials for electronic devices, including two-dimensional materials, two-dimensional electron gas, multiferroic materials, memory materials, sensor materials, and spintronic materials. Describes the basics as well as new developments of these functional materials and devices.
Book Synopsis Spin Electronics by : David D. Awschalom
Download or read book Spin Electronics written by David D. Awschalom and published by Springer Science & Business Media. This book was released on 2004 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a comparative review of spin electronics ("spintronics") research and development activities in the United States, Japan, and Western Europe conducted by a panel of leading U.S. experts in the field. It covers materials, fabrication and characterization of magnetic nanostructures, magnetism and spin control in magnetic nanostructures, magneto-optical properties of semiconductors, and magneto electronics and devices. Spin Electronics is unique in that it combines tutorial and introductory information on the significance of spin electronics research and applications development in this rapidly developing field. It reviews profound technical and policy implications of spin-based devices for the future of semiconductor electronics, non-volatile computer memory, nanotechnology, and quantum computing and communications. For example, the report discusses the potential for spin electronics to help maintain the progress in price and performance of electronics and computers described in Moore's Law. Finally, information on funding and level of effort in the laboratories visited by the panel is provided.
Book Synopsis Advanced Magnetic Nanostructures by : D.J. Sellmyer
Download or read book Advanced Magnetic Nanostructures written by D.J. Sellmyer and published by Springer Science & Business Media. This book was released on 2006-07-02 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced magnetic nanostructures is an emerging field in magnetism and nanotechnology, but the literature consists of a rich variety of original papers and parts of reviews and books whose scope is comparatively broad. This calls for a book with specific emphasis on state-of-the-art synthetic methods for fabricating, characterizing and theoretically modeling new magnetic nanostructures. This book is intended to provide a comprehensive overview of the present state of the field. Leading researchers world-wide have contributed a survey of their special ties to guide the reader through the exploding literature in nanomagnetic structures. The focus is on deliberately structured nanomagnets. It includes cluster assembled, self-organized and patterned thin films but excludes, for example, multilayered thin films. We target both industrial and academic researchers in magnetism and related areas, such as nanotechnology, materials science, and theoretical solid-state physics.
Book Synopsis Spin Dependent Transport in Magnetic Nanostructures by : Sadamichi Maekawa
Download or read book Spin Dependent Transport in Magnetic Nanostructures written by Sadamichi Maekawa and published by CRC Press. This book was released on 2002-07-11 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: In magnetic systems of nano-meter size, the interplay between spin and charge of electrons provides unique transport phenomena. In magnetic superlattices, magnetic and non-magnetic metallic thin films with thickness of the order of one nano-meter are piled-up alternately. Since the discovery of giant magnetoresistance (GMR) in these superlattices in 1988, spin dependent transport phenomena in magnetic nanostructures have received much attention from both academic and technological points of view. Ferromagnetic tunnel junctions made of ferromagnetic metal electrodes and a very thin insulating barrier between them are also of current interest as magnetoresistive devices, where the tunneling current depends on the relative orientation of magnetization (TMR). In addition to magnetic superlattices and magnetic tunnel junctions, magnetic granular systems and magnetic dots have been studied extensively as magnetoresistive systems. Edited by two of the world's leading authorities, Spin Dependent Transport in Magnetic Nanostructures introduces and explains the basic physics and applications of a variety of spin-dependent transport phenomena in magnetic nanostructures with particular emphasis on magnetic multilayers and magnetic tunnel junctions.
Book Synopsis Magnetic Nanostructures in Modern Technology by : Bruno Azzerboni
Download or read book Magnetic Nanostructures in Modern Technology written by Bruno Azzerboni and published by Springer Science & Business Media. This book was released on 2007-10-22 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, a team of outstanding scientists in the field of modern magnetic nanotechnologies illustrates the state-of-the-art in several areas of advanced magneto-electronic devices, magnetic micro-electromechanical systems and high density information storage technologies. Providing a unique source of information for the young physicist, chemist or engineer, the book also serves as a crucial reference for the expert scientist and the teacher of advanced university courses.
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 Spin Transfer Torque Effects and Spin Relaxation in Magnetic Nanostructures by : Xiaojun Wang
Download or read book Spin Transfer Torque Effects and Spin Relaxation in Magnetic Nanostructures written by Xiaojun Wang and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Manipulation of Magnetic Moment Using the Spin Current from Magnetic and Non-magnetic Materials by : Luqiao Liu
Download or read book Manipulation of Magnetic Moment Using the Spin Current from Magnetic and Non-magnetic Materials written by Luqiao Liu and published by . This book was released on 2012 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis summarizes my studies on the effect of spin transfer torque on metallic ferromagnets. The spin current for generating the spin torque is either from ferromagnetic electrode through the spin filtering effect, or from nonmagnetic material through the spin Hall effect (SHE). In the experiment using the spin filtering effect, the current flows vertically through the nanoscale spin valve geometries. I will describe the fabrication process that I used to make the nanopillar structure and the strategy that I developed to reduce the critical current. In the experiment utilizing the SHE, the current flows within the film plane and the spin current is injected transversely from the non-magnetic (NM) film into the adjacent ferromagnetic (FM) layer. I will present five studies that I made to characterize the properties of the SHE and its influence on the magnetic moment. In the first study, I employed the spin torque ferromagnetic resonance (FMR) technique to determine the spin Hall angle. In this experiment, radio frequency current was applied onto the NM/FM bilayer and FMR was induced by the resultant oscillating spin current. By looking into the amplitude of the FMR signal, I was able to get the value of the spin Hall angle. In the second and third studies, I demonstrated that the SHE could be utilized to switch magnetic moment of both perpendicularly and in-plane magnetized FM films. For the perpendicular case, the spins injected into the FM film exert a torque that is perpendicular to the equilibrium position of the moment and it fights against the restoring anisotropy field and induces switching. For the in-plane case, the spins cause switching through the anti-damping mechanism. In the fourth study, I showed that the SHE could induce persistent magnetic oscillations. DC spin current reduces the magnetic damping to zero and the moment undergoes precession around the applied magnetic field. In the final study, I demonstrated that the SHE switching current can be modulated by the electric field applied across the FM/oxide barrier. The electric field modifies the anisotropy of the free FM layer and alters the critical current correspondingly.
