Download or read book Imaging and Control of Magnetization Dynamics for Spintronic Devices written by Daniel Birt and published by . This book was released on 2013 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: As features on integrated circuits continue to shrink, currently at 22 nm and predicted to approach 10 nm by 2020, the semiconductor industry is rapidly brushing up against the fundamental limits of electric charge and current based devices. These limits are due to the fact that charges are being pushed around in tiny areas and they repel one another with significant force. Fortunately, there are many other degrees of freedom in solids that do not suffer from these limitations and are just waiting to be harnessed in useful devices. This idea is behind all of the fields that have lately been proliferating ending in -onics, photonics, plasmonics, phononics, and of most relevance to this dissertation spintronics. Spintronics refers to a field of research wherein ways are sought to utilize the spin property of the electron in devices. One of the most attractive aspects of electron spin is that it can be used to store (transiently or permanently), process, and transmit information. The main challenge in spintronics is accessing the spin degree of freedom. Until the discovery of the giant magnetoresistance effect in the late 1980's, the only way to manipulate the electron spin was through a magnetic field. Recent developments have shown that electron spins can be controlled with direct currents of both heat and electrons, which have the benefit of being easy to generate and direct without interfering over a large area. The purpose of this dissertation is to study methods of controlling the dynamics of magnetization in thin films for spintronic applications by imaging the spin wave intensity in devices. To this end we have constructed a micro-focus Brillouin Light Scattering system to map the intensity of spin waves propagating in thin ferromagnetic films on the sub-micron scale. We have studied issues relating to fundamental issues of spin wave propagation in thin films. We have investigated the possibility of spin wave amplification with direct charge currents and spin currents generated by the spin Hall effect. Furthermore, we have demonstrated the ability to measure the magnon and phonon temperatures, which is important for studies of thermal transport.
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 Interactions Between Spin Transport and Dynamics Studied Using Spatially Resolved Imaging and Magnetic Resonance written by Michael Roy Page and published by . This book was released on 2016 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, I explore the interactions that occur between transported spins and magnetization dynamics using spatially resolved imaging and magnetic resonance. The integration of spin transport and dynamics will be a crucial aspect of realizing spintronic devices, which seek to improve upon current charge based electronics. Rather than focusing on the charge degree of freedom as in traditional electronics, spintronics seeks to utilize the properties of the electron spin degree of freedom to revolutionize the fundamental operating principles of data processing and storage devices. Spintronics promises greater functionality and energy efficiency in devices based on electron spin. However, improved understanding and control of the spin degree of freedom is required for spintronics to reach its full potential. The work in this dissertation represents efforts towards addressing these requirements. I discuss my work relating to the development of a custom scanned probe microscope allowing simultaneous spatially resolved imaging while imposing transport in electrically active spintronic devices. Using this microscope, I correlate the switching of magnetic electrodes in a graphene spin valve to the resistance states by directly imaging the electrode magnetization configuration while simultaneously measuring the non-local magnetoresistance. I investigate interactions between a ferromagnet driven into resonance and proximal nitrogen vacancy centers in diamond. Spinwaves generated during the decay of the uniform mode driven to ferromagnetic resonance relax the diamond nitrogen vacancy center spins resulting in a change in the fluorescence intensity. This technique allows the study of transport of angular momentum between two separated spin systems, as well as the possibility for the nanoscale imaging of magnetization dynamics. I demonstrate Heusler alloy ferromagnetic materials as high spin polarization spin injectors for device applications by studying their magnetoresistive output as a function of composition at room and low temperatures. Spin injection efficiency is another important aspect in the performance of spintronic devices, and optimization of spin injection will be of importance in creating realistic devices. Another promising avenue for spin injection relies on the spin Hall effect. I discuss efforts at using the spin Hall effect in platinum to inject spins into an aluminum channel to be detected in another platinum electrode by the inverse spin Hall effect without the need for a ferromagnet, thus reducing complications resulting from the stray field of typical ferromagnetic injectors. I discuss exploration of spin pumping devices based on metallic and insulating ferromagnet/graphene bilayers using ferromagnetic resonance and electrical detection of the inverse spin Hall effect. Spin pumping represents another opportunity to study interactions of spin transport and magnetization dynamics, in this case leveraged for efficient spin injection. Finally, I perform magnetic resonance measurements of thin film iron germanium skyrmionic candidate materials. Skrymions are a candidate for high density and low power magnetic recording. Measuring the dynamics of these materials will be important for a full characterization of their properties. I demonstrate detection of multiple magnetic phases in this material, and show evidence of large internal fields, which may be of interest in stabilizing skrymions in thin films.
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 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 Magnetism and Accelerator Based Light Sources written by Hervé Bulou and published by Springer Nature. This book was released on 2021-02-17 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book collects the contributions of the seventh school on Magnetism and Synchrotron Radiation held in Mittelwihr, France, from 7 to 12 October 2018. It starts with an introduction to the physics of modern X-ray sources followed by a general overview of magnetism. Next, light / matter interaction in the X-ray range is covered with emphasis on different types of angular dependence of X-ray absorption spectroscopy and scattering. In the end, two domains where synchrotron radiation-based techniques led to new insights in condensed matter physics, namely spintronics and superconductivity, are discussed. The book is intended for advanced students and researchers to get acquaintance with the basic knowledge of X-ray light sources and to step into synchrotron-based techniques for magnetic studies in condensed matter physics or chemistry.
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 Magnetization Dynamics in Spin Valves written by Frederik Wegelin and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2010-04 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: Key technology applications like magnetoresistive sensors or the Magnetic Random Access Memory (MRAM) require reproducible magnetic switching mechanisms. i.e. predefined remanent states. At the same time advanced magnetic recording schemes push the magnetic switching time into the gyromagnetic regime. Objects of study in this study are antiparallel pinned synthetic spin valves as they are extensively used as read heads in today's magnetic storage devices. Results are reported of element specific Time Resolved Photo Emission Electron Microscopy (TR PEEM) to image the magnetization dynamics of the free layer alone via X ray Circular Dichroism (XMCD). The observation of magnetic switching processes in the gigahertz range became possible due to the joined effort of producing ultra short X ray pulses at BESSY II and optimizing the wave guide design of the samples for high frequency electromagnetic excitation. It could be shown that the magnetization dynamics of the free layer of a GMR spin valve stack deviates significantly from a simple phase coherent rotation."
Download or read book Magnetization Dynamics in Spintronic Structures and Devices written by and published by . This book was released on 2006 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spin Current Induced Control of Magnetization Dynamics written by Martin Maria Decker and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Magnetism of Surfaces Interfaces and Nanoscale Materials written by Robert E. Camley and published by Elsevier. This book was released on 2015-10-27 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past 30 years, magnetic research has been dominated by the question of how surfaces and interfaces influence the magnetic and transport properties of nanostructures, thin films and multilayers. The research has been particularly important in the magnetic recording industry where the giant magnetoresistance effect led to a new generation of storage devices including hand-held memories such as those found in the ipod. More recently, transfer of spin angular momentum across interfaces has opened a new field for high frequency applications.This book gives a comprehensive view of research at the forefront of these fields. The frontier is expanding through dynamic exchange between theory and experiment. Contributions have been chosen to reflect this, giving the reader a unified overview of the topic. Addresses both theory and experiment that are vital for gaining an essential understanding of topics at the interface between magnetism and materials science Chapters written by experts provide great insights into complex material Discusses fundamental background material and state-of-the-art applications, serving as an indispensable guide for students and professionals at all levels of expertise Stresses interdisciplinary aspects of the field, including physics, chemistry, nanocharacterization, and materials science Combines basic materials with applications, thus widening the scope of the book and its readership
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 Ultrafast Manipulation of Magnetic Order with Electrical Pulses written by Yang Yang and published by . This book was released on 2005 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last 30 years spintronics has been a very rapidly expanding field leading to lots of new interesting physics and applications. As with most technology-oriented fields, spintronics strives to control devices with very low energy consumption and high speed. The combination of spin and electronics inherent to spintronics directly tackles energy efficiency, due to the non-volatility of magnetism. However, speed of operation of spintronic devices is still rather limited (~nanoseconds), due to slow magnetization precessional frequencies. Ultrafast magnetism (or opto-magnetism) is a relatively new field that has been very active in the last 20 years. The main idea is that intense femtosecond laser pulses can be used in order to manipulate the magnetization at very fast time-scales (~100 femtoseconds). However, the use of femtosecond lasers poses great application challenges such as diffraction limited optical spot sizes which hinders device density, and bulky and expensive integration of femtosecond lasers into devices. In this thesis, our efforts to combine ultrafast magnetism and spintronics are presented. First, we show that the magnetization of ferrimagnetic GdFeCo films can be switched by picosecond electronic heat current pulses. This result shows that a non-thermal distribution of electrons directly excited by laser is not necessary for inducing ultrafast magnetic dynamics. Then, we fabricate photoconductive switch devices on a LT-GaAs substrate, to generate picosecond electrical pulses. Intense electrical pulses with 10ps (FWHM) duration and peak current up to 3A can be generated and delivered into magnetic films. Distinct magnetic dynamics in CoPt films are found between direct optical heating and electrical heating. More importantly, by delivering picosecond electrical pulses into GdFeCo films, we are able to deterministically reverse the magnetization of GdFeCo within ~10ps. This is more than one order of magnitude faster than any other electrically controlled magnetic switching. Our results present a fundamentally new switching mechanism electrically, without requirement for any spin polarized current or spin transfer/orbit torques. Our discovery that ultrafast magnetization switching can be achieved with electrical pulses will launch a new frontier of spintronics science and herald a new generation of spintronic devices that operate at high speed with low energy consumption. At last, to push ultrafast spintronics to practical use, ultrafast switching of a ferromagnetic film is desired. By exploiting the exchange interaction between GdFeCo and ferromagnetic Co/Pt layer, we achieved ultrafast (sub 10ps) switching of ferromagnetic film with a single laser pulse. This result will open up the possibility to control ferromagnetic materials at ultrafast time scale, critical for practical applications.
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 Introduction to Spintronics written by Supriyo Bandyopadhyay and published by CRC Press. This book was released on 2008-03-20 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using spin to replace or augment the role of charge in signal processing devices, computing systems and circuits may improve speed, power consumption, and device density in some cases—making the study of spinone of the fastest-growing areas in micro- and nanoelectronics. With most of the literature on the subject still highly advanced and heavily theoretical, the demand for a practical introduction to the concepts relating to spin has only now been filled. Explains effects such as giant magnetoresistance, the subject of the 2007 Nobel Prize in physics Introduction to Spintronics is an accessible, organized, and progressive presentation of the quantum mechanical concept of spin. The authors build a foundation of principles and equations underlying the physics, transport, and dynamics of spin in solid state systems. They explain the use of spin for encoding qubits in quantum logic processors; clarify how spin-orbit interaction forms the basis for certain spin-based devices such as spintronic field effect transistors; and discuss the effects of magnetic fields on spin-based device performance. Covers active hybrid spintronic devices, monolithic spintronic devices, passive spintronic devices, and devices based on the giant magnetoresistance effect The final chapters introduce the burgeoning field of spin-based reversible logic gates, spintronic embodiments of quantum computers, and other topics in quantum mechanics that have applications in spintronics. An Introduction to Spintronics provides the knowledge and understanding of the field needed to conduct independent research in spintronics.
Download or read book Spintronics written by Tomasz Blachowicz and published by Walter de Gruyter GmbH & Co KG. This book was released on 2019-05-06 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting from quantum mechanical and condensed matter foundations, this book introduces into the necessary theory behind spin electronics (Spintronics). Equations of spin diffusion, -evolution and -tunelling are provided before an overview is given of simulation of spin transport at the atomic scale. Furthermore, applications are discussed with a focus on elementary spintronics devices such as spin valves, memory cells and hard disk heads.
