Download or read book Magnetic Dynamics in Magnetic Multilayers and Spintronic Devices written by Hang Chen and published by . This book was released on 2021 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: A critical issue in spintronic devices is how to efficiently switch the magnetization of a nanomagnet. The switching is typically occurred at ferromagnetic resonant frequency. One of the very desired features is to enhance the resonant frequency so as to increase the switching speed. In this thesis. we use optical mode in coupled FM bilayers to significantly enhance the resonance frequency because the ferromagnetic exchange coupling is much stronger compared with other effective field introduced by, for example, strain or anisotropy. we theoretically and experimentally study the resonant frequency in Co90Fe10/Ta/(Ni80Fe20)18́2xCux trilayer. we also validate the theoretical model with experimental results and use the theoretical model to further design heterostructures with desired properties such as enhanced intensity in OM. All of our experimental results are fully explained by our model which also allows us to identify the coupling mechanism as Neel "orange-peel" coupling and extract the interlayer coupling strength. In current magnetic random access memories (MRAMs), the magnetization is switched via spin transfer torques (STT) or spin orbit torques (SOTs). In this thesis, we use a time-resolved (TR) Magneto-optic Kerr effect (TRMOKE) to investigate the SOT-induced magnetization dynamics in Py/Pt and Ta/CoFeB heterostructures. We have answered three questions as we set to explore: (1) the field-like torque determines initial oscillation magnitude and the damping-like torque determines the final steady position; (2) both the effect field of damping-like toque hDL and field-like torque hFL can be extracted from the TRMOKE spectrum, and (3) the ratio hDL/ hFL measured from dynamics are the same as those measured at low frequency. Finally, we also explore the way of using voltage to switch the magnetization in order to significantly reduce the energy consumption. We employed an antiferromagnetic Cr2O3 film with net a net magnetization at the film surface. The surface magnetization can be isothermally switched via applied electric field (voltage), enabling "writing" function in the memory cell. We solved various challenges in developing the final device including (1) exchange coupling between the surface magnetization and the magnetization in a ferromagnetic heterostructure of Co/Pd multilayer, (2) the exchange coupling between Co/Pd and CoFeB which has perpendicular magnetization and serves as a bottom electrode of magnetic tunnel junction for readout. (3) the leakage issue of Cr2O3, (4) the contact to middle layer that is less than 5 nm thick, and (5) device layout and detailed fabrication steps. Although we did not have time to fully demonstrate the devices, all key steps have been well resolved.
Download or read book Spintronics written by Puja Dey and published by Springer Nature. This book was released on 2021-04-13 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the overview of Spintronics, including What is Spintronics ?; Why Do We Need Spintronics ?; Comparative merit-demerit of Spintronics and Electronics ; Research Efforts put on Spintronics ; Quantum Mechanics of Spin; Dynamics of magnetic moments : Landau-Lifshitz-Gilbert Equation; Spin-Dependent Band Gap in Ferromagnetic Materials; Functionality of ‘Spin’ in Spintronics; Different Branches of Spintronics etc. Some important notions on basic elements of Spintronics are discussed here, such as – Spin Polarization, Spin Filter Effect, Spin Generation and Injection, Spin Accumulation, Different kinds of Spin Relaxation Phenomena, Spin Valve, Spin Extraction, Spin Hall Effect, Spin Seebeck Effect, Spin Current Measurement Mechanism, Magnetoresistance and its different kinds etc. Concept of Giant Magnetoresistance (GMR), different types of GMR, qualitative and quantitative explanation of GMR employing Resistor Network Theory are presented here. Tunnelling Magnetoresistance (TMR), Magnetic Junctions, Effect of various parameters on TMR, Measurement of spin relaxation length and time in the spacer layer are covered here. This book highlights the concept of Spin Transfer Torque (STT), STT in Ferromagnetic Layer Structures, STT driven Magnetization Dynamics, STT in Magnetic Multilayer Nanopillar etc. This book also sheds light on Magnetic Domain Wall (MDW) Motion, Ratchet Effect in MDW motion, MDW motion velocity measurements, Current-driven MDW motion, etc. The book deals with the emerging field of spintronics, i.e., Opto-spintronics. Special emphasis is given on ultrafast optical controlling of magnetic states of antiferromagnet, Spin-photon interaction, Faraday Effect, Inverse Faraday Effect and outline of different all-optical spintronic switching. One more promising branch i.e., Terahertz Spintronics is also covered. Principle of operation of spintronic terahertz emitter, choice of materials, terahertz writing of an antiferromagnetic magnetic memory device is discussed. Brief introduction of Semiconductor spintronics is presented that includes dilute magnetic semiconductor, feromagnetic semiconductor, spin polarized semiconductor devices, three terminal spintronic devices, Spin transistor, Spin-LED, and Spin-Laser. This book also emphasizes on several modern spintronics devices that includes GMR Read Head of Modern Hard Disk Drive, MRAM, Position Sensor, Biosensor, Magnetic Field sensor, Three Terminal Magnetic Memory Devices, Spin FET, Race Track Memory and Quantum Computing.
Download or read book Nonlocal and Local Magnetization Dynamics Excited by an RF Magnetic Field in Magnetic Multilayers written by Takahiro Moriyama and published by ProQuest. This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A microwave study in spintronic devices has been actively pursued in the past several years due to the fertile physics and potential applications. On one hand, a passive use of microwave can be very helpful to analyze and understand the magnetization dynamics in spintronic devices. Examples include ferromagnetic resonance (FMR) measurements, and various microwave spectrum analyses in ferromagnetic materials. The most important chrematistic parameter for the phenomenological analysis on the magnetization dynamics is, so called, the Gilbert damping constant. In this work, a relatively new measurement technique, a flip-chip FMR measurement, to conduct the ferromagnetic resonance measurements has been developed. The measurement technique is equally comparable to a conventional FMR measurement. The Gilbert damping constants were extracted for single ferromagnetic layer, spin vale structures, and magnetic tunnel junctions (MTJs). On the other hand, an active use of microwave yields a great potential for interesting phenomena which give new functionalities into spintronic devices. For instance, a spin wave excitation by an rf field can be used to reduce the switching field of a ferromagnet, i.e. microwave assisted magnetization reversal, which could be a potential application in advanced recording media. More interestingly, a precessing magnetization driven by an rf field can generate a pure spin current into a neighboring layer, i.e. spin pumping effect, which is one of the candidates for generating a pure spin current. A ferromagnetic tunnel junction (MTJ) is one of the important devices in spintronics, which is also the key device to investigate the local and nonlocal magnetization dynamics in this work. Therefore, it is also important to develop high quality MTJs. My work starts from the development of MTJ with AlOx and MgO tunnel barriers where it was found it is crucial to find the proper condition for forming a few nanometers thick tunnel barrier. After obtaining quality MTJs, we proceeded to the study on magnetization dynamics using the MTJs. First interesting phenomenon found in this work is the microwave assisted magnetization reversal (MAMR). It is found that magnetization reversal can be achieved efficiently by an appropriate power and frequency microwave. Moreover, there is a mutual relationship between microwave power and frequency for achieving a maximum switching field reduction. This effect can be very useful in magnetic data storage device which essentially needs to reduce the "effective" coercivity field. In the study of nonlocal magnetization dynamics, we tried to detect the spin accumulation induced by spin pumping effect in FM/NM/I/FM, FM/I/NM and FM/I/FM structures with a microwave excitation (FM: ferromagnetic material, NM: nonmagnetic material, and I: tunnel barrier). Interestingly, in the FM/I/NM and FM/I/FM structures, we observed ~mu-V dc voltage due to the precessing magnetizations. It is found that the dc voltage we observed is much larger than the current the spin pumping theory predicts. Therefore we speculated a new mechanism to explain the results. Although we discussed only a portion of the magnetization dynamics involving nonlinear and nonequilibrium phenomena, it reveals that there is still a fertile physics which has not yet been investigated or explained.
Download or read book Spin Dynamics in Magnetic Thin Films and Spintronics Devices written by Yunpeng Chen and published by . This book was released on 2016 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic materials are the essential parts of advanced magnetic recording and microwave devices. All the applications require the control of the magnetization orientation that is studied as magnetic dynamics. In a magnetic recording device, such as hard disk drive (HDD), the digital information is stored as the magnetization direction of magnetic domains. To rewrite the information, one needs to reverse the magnetization. With the increase of areal density, the magnetic anisotropy is enhanced to overcome the thermal fluctuations. Consequently, the magnetic switching becomes more difficult. Microwave assisted magnetization reversal (MAMR) is developed to lower the switching field by exciting large angle precession of magnetization. Damping constant, as a parameter describing the dissipation of magnetic materials, plays a critical role in MAMR. In this thesis, I theoretically and experimentally study the damping dependence of MAMR in micro-size magnetic dots. Based on the study, MAMR is more efficient when the damping of the magnetic dot is small. Magnetic random access memory (MRAM) based on magnetic tunnel junctions (MTJs) is a novel magnetic recording device that has the potential to replace HDD due to its fast read/write rate. Moreover, to keep increasing the recording density, the magnetic media with perpendicular magnetic anisotropy (PMA) replaced the in-plane magnetic recording media. In this work, the magnetic thin films such as Co/Pd multilayers and Ta/CoFeB/MgO were fabricated to be with PMA. Based on the PMA thin films, the MTJs were developed with optimized deposition conditions and post-annealing. We observed above 60% TMR in Ta/CoFeB/MgO/CoFeB based perpendicular junctions. The voltage controlled magnetic anisotropy (VCMA) was demonstrated in those MTJs, which is an efficient technique to control the magnetization via an electric field. The spin transfer torques were also characterized in Ta/CoFeB/MgO structures with PMA. The microwave response is another useful property of magnetic materials. The ferromagnetic resonance (FMR) of typical ferromagnetic materials like Fe, Co, Ni and their alloys are in the gigahertz range. Therefore, the magnetic thin films have been widely utilized in microwave devices such as bandpass filters, insulators, and oscillators. Conventionally, electromagnets generate a magnetic field to control the resonance frequency, which is bulky, noisy, slow and energy consuming. By realizing the huge effective field due to exchange interaction, a novel scheme was demonstrated to shift the resonance frequency of the optical mode in magnetic bilayers with interlayer exchange interaction. A maximum 20 GHz tunable range was achieved in a spin-valve base spintronics microwave device in the experiment. A dynamic tuning of the resonance frequency as high as 9 GHz was demonstrated via temperature controlled exchange interaction.
Download or read book Nanomagnetism and Spintronics written by Teruya Shinjo and published by Elsevier. This book was released on 2009-06-29 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spintronics is a newly developing area in the field of magnetism, in which the interplay of magnetism and transport phenomena is studied experimentally and theoretically. This book introduces the recent progresses in the research relating to spintronics. Presents in-depth analysis of this fascinating and technologically important new branch of nanoscience Edited text with contributions from acknowledged leaders in the field This handbook and guide will appeal to students and researchers in the fields of electronic devices and materials
Download or read book Magnetic Nanostructures in Modern Technology written by Bruno Azzerboni and published by Springer. This book was released on 2007-10-14 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.
Download or read book Femtosecond Spin Dynamics in Magnetic Multilayers Employing High Harmonics of Laser Radiation written by Denis Rudolf and published by Forschungszentrum Jülich. This book was released on 2013 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spintronics Handbook Second Edition Spin Transport and Magnetism written by Evgeny Y. Tsymbal and published by CRC Press. This book was released on 2019-05-09 with total page 735 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spintronics Handbook, Second Edition offers an update on the single most comprehensive survey of the two intertwined fields of spintronics and magnetism, covering the diverse array of materials and structures, including silicon, organic semiconductors, carbon nanotubes, graphene, and engineered nanostructures. It focuses on seminal pioneering work, together with the latest in cutting-edge advances, notably extended discussion of two-dimensional materials beyond graphene, topological insulators, skyrmions, and molecular spintronics. The main sections cover physical phenomena, spin-dependent tunneling, control of spin and magnetism in semiconductors, and spin-based applications.
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 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.
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
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.
Download or read book Nanomagnetism and Spintronics written by Teruya Shinjo and published by Elsevier Inc. Chapters. This book was released on 2013-10-07 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: This overview is a brief introduction to the subjects covered by this book, nanomagnetism and spintronics. The discovery of giant magnetoresistance (GMR) effect is described together with a short summary of the studies prior to the experiments on GMR. Studies on various kinds of magnetoresistance (MR) effect that were inspired by the GMR effect are reviewed and recent topics are introduced. In many novel phenomena involving the interplay of electric conductance and magnetization, the role of the “spin current” has been revealed to be important and the possibility for exploiting these phenomena in spintronics devices has been suggested. Nanoscale devices are indispensable to fundamental studies on spintronics and also to various technical devices, and therefore gaining an understanding of nanomagnetism is a crucial current issue. At the end of this section, the scope of this book is described in brief with the content of each chapter.
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.
Download or read book Magnetization Dynamics in Ultrathin Films and Multilayers written by Arjun Sapkota and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Robust understanding of magnetization dynamics is very crucial to design and fabricate novelmaterials for next generation spintronic applications. A combination of experimental techniques and theoretical modeling facilitates fundamental research to establish new concepts. This dissertation discusses the magnetization dynamics of ultrathin films and multilayers using broadband ferromagnetic resonance (FMR) techniques and micromagnetic simulations. Chapter one includes the theoretical background on magnetization dynamics, the explanation of FMR experiments with schematic diagrams and data analysis, and insight in micromagnetic simulations using the in-house developed MATLAB-based code M^3. All simulations are performed with M^3. Chapter one also includes a summary of various publications which I co-authored during my time as a graduate student in the Mewes Magnetics Laboratory at UA. Chapter two discusses the limitations of the macrospin model of materials with inhomogeneous perpendicular anisotropy. This is a micromagnetic study motivated from experimental FMR measurements of [Co/Ni]_N multilayers. Chapter three is devoted to experimental FMR measurements carried out on FeGa thin films. These results show significantly lower Gilbert damping and linewidth in comparison to previous publications in similar structures, indicating the high quality of these thin films. This is also confirmed by X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements. These films are particularly interesting because of their well known superior magnetostrictive behavior. Motivated from previous FMR experiments in IrMn/CoFe and MnN/CoFeB exchange bias systems, we investigated the anisotropic damping in multilayer spintronic devices using micromagnetic simulations in chapter four. With the introduction of a damping tensor in the Landau-Lifshitz- Gilbert (LLG) equation, this study explains the observed unidirectional relaxation in IrMn/CoFe bilayers and co-existence of unidirectional and uniaxial relaxation in MnN/CoFeB bilayers .
Download or read book Magnetic Anisotropies and Dynamic Magnetic Properties in Multilayered Thin Films written by Jamileh Beik Mohammadi and published by . This book was released on 2017 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical and experimental research on magnetic materials and magnetic devices intend to investigate novel materials and structures which can be used for the next generation spintronic devices. Moreover, it is essential to conduct fundamental research on new phenomena aiming for new generation of devices that can be faster, smaller, cheaper, and more reliable. Magnetic anisotropies have been widely used in spintronic devices. From the unidirectional exchange bias anisotropy that is used in magnetic read heads and giant magnetic resonance (GMR) sensors, to the interfacial perpendicular magnetic anisotropy (PMA) that is essential for magnetic tunnel junctions (MTJs). In the first chapter of this dissertation a short introduction to magnetization dynamics including experimental techniques is given. In the second chapter, the exchange bias anisotropy and the interfacial origin of relaxation in Ru/IrMn/CoFe/Ru exchange biased systems is discussed and investigated. The interfacial perpendicular anisotropy is observed in these systems and can be quantified using FMR technique. Such anisotropy can exist in a thin ferromagnetic film (such as NiFe) that is in proximity to a metallic (e.g.Ru) or insulating (e.g. SiO2) non-magnetic layer, which is the topic of the third chapter of this dissertation. In addition, experimental results confirm that spatial fluctuations of the uniaxial perpendicular anisotropy can push the easy axis of the magnetization in an orientation that is neither perpendicular to the film nor normal to it. The effect of the lateral fluctuation of the uniaxial anisotropy on the magnetic energy landscape and the magnetization dynamics of thin magnetic layers is reported in chapter four using micromagnetic simulations.
Download or read book Spin Current written by Sadamichi Maekawa and published by Oxford University Press. This book was released on 2017-09-29 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the discovery of the giant magnetoresistance (GMR) effect in magnetic multilayers in 1988, a new branch of physics and technology, called spin-electronics or spintronics, has emerged, where the flow of electrical charge as well as the flow of electron spin, the so-called "spin current", are manipulated and controlled together. Recent progress in the physics of magnetism and the application of spin current has progressed in tandem with the nanofabrication technology of magnets and the engineering of interfaces and thin films. This book is intended to provide an introduction and guide to the new physics and applications of spin current. The emphasis is placed on the interaction between spin and charge currents in magnetic nanostructures.
