Spin Transfer Torque Magnetisation Switching In Mgo Based Magnetic Tunnel Junctions
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Spin Transfer Torque Magnetisation Switching In Mgo Based Magnetic Tunnel Junctions
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Author : Kaan Oguz
language : en
Publisher:
Release Date : 2010
Spin Transfer Torque Magnetisation Switching In Mgo Based Magnetic Tunnel Junctions written by Kaan Oguz and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Characterization Of Spin Transfer Torque And Magnetization Manipulation In Magnetic Nanostructures
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Author : Chen Wang
language : en
Publisher:
Release Date : 2012
Characterization Of Spin Transfer Torque And Magnetization Manipulation In Magnetic Nanostructures written by Chen Wang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
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.
Spin Transfer Torques In Mgo Based Magnetic Tunnel Junctions
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Author : Kerstin Bernert
language : en
Publisher:
Release Date : 2014
Spin Transfer Torques In Mgo Based Magnetic Tunnel Junctions written by Kerstin Bernert and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Magnetic Memory Technology
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Author : Denny D. Tang
language : en
Publisher: John Wiley & Sons
Release Date : 2021-01-07
Magnetic Memory Technology written by Denny D. Tang and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-01-07 with Science categories.
STAY UP TO DATE ON THE STATE OF MRAM TECHNOLOGY AND ITS APPLICATIONS WITH THIS COMPREHENSIVE RESOURCE Magnetic Memory Technology: Spin-Transfer-Torque MRAM and Beyond delivers a combination of foundational and advanced treatments of the subjects necessary for students and professionals to fully understand MRAM and other non-volatile memories, like PCM, and ReRAM. The authors offer readers a thorough introduction to the fundamentals of magnetism and electron spin, as well as a comprehensive analysis of the physics of magnetic tunnel junction (MTJ) devices as it relates to memory applications. This book explores MRAM's unique ability to provide memory without requiring the atoms inside the device to move when switching states. The resulting power savings and reliability are what give MRAM its extraordinary potential. The authors describe the current state of academic research in MRAM technology, which focuses on the reduction of the amount of energy needed to reorient magnetization. Among other topics, readers will benefit from the book's discussions of: An introduction to basic electromagnetism, including the fundamentals of magnetic force and other concepts An thorough description of magnetism and magnetic materials, including the classification and properties of magnetic thin film properties and their material preparation and characterization A comprehensive description of Giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR) devices and their equivalent electrical model Spin current and spin dynamics, including the properties of spin current, the Ordinary Hall Effect, the Anomalous Hall Effect, and the spin Hall effect Different categories of magnetic random-access memory, including field-write mode MRAM, Spin-Torque-Transfer (STT) MRAM, Spin-Orbit Torque (SOT) MRAM, and others Perfect for senior undergraduate and graduate students studying electrical engineering, similar programs, or courses on topics like spintronics, Magnetic Memory Technology: Spin-Transfer-Torque MRAM and Beyond also belongs on the bookshelves of engineers and other professionals involved in the design, development, and manufacture of MRAM technologies.
Spin Orbit Torque Driven Magnetic Switching For Low Power Computing And Memory
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Author : Debanjan Bhowmik
language : en
Publisher:
Release Date : 2015
Spin Orbit Torque Driven Magnetic Switching For Low Power Computing And Memory written by Debanjan Bhowmik and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Spintronics has rapidly emerged as a highly pursued research area in solid-state physics and devices owing to its potential application in low power memory and logic as well as the rich physics associated with it. Traditionally in spintronics, spin transfer torque in magnetic tunnel junctions and spin valves has been used to manipulate ferromagnets. Spin orbit torque has recently emerged as an alternative mechanism for manipulating such ferromagnets, which offers advantages of lower energy consumption, simpler device structure, etc. For a ferromagnet- heavy metal bilayer, electrons flowing through the heavy metal separate based on the direction of their spin. This results in the accumulation of spin polarized electrons at the interface, which in turn applies a torque, known as spin orbit torque, on the ferromagnet. A typical such heavy metal is tantalum (Ta) and typical such ferromagnet is CoFeB. The research presented in this dissertation shows how in a perpendicularly polarized Ta/CoFeB/MgO heterostructure, spin orbit torque at the interface of the Ta and CoFeB layers can be used to manipulate the magnetic moments of the CoFeB layer for low power memory and logic applications. The main results presented in this dissertation are fourfold. First, we report experiments showing spin orbit torque driven magnetic switching in a perpendicularly polarized Ta/CoFeB/MgO heterostructure and explain the microscopic mechanism of the switching. Using that microscopic mechanism, we show a new kind of ferromagnetic domain wall motion. Traditionally a ferromagnetic domain wall is known to flow parallel or antiparallel to the direction of the current, but here we show that spin orbit torque, owing to its unique symmetry, can be used to move the domain wall orthogonal to the current direction. Second, we experimentally demonstrate the application of this spin orbit torque driven switching in nanomagnetic logic, which is a low power alternative to CMOS based computing. Previous demonstrations of nanomagnetic logic needed an external magnetic field, the generation of which needed a large amount of current rendering such logic scheme uncompetitive compared to its CMOS counterpart. Here we show that spin orbit torque eliminates the need of an external magnetic field for nanomagnetic logic and hence spin orbit torque driven nanomagnetic logic consumes 100 times lower current than magnetic field driven nanomagnetic logic at room temperature. Though we can demonstrate magnetic logic with spin orbit torque in the absence of the magnetic field, spin orbit torque driven deterministic switching of a perpendicular magnet from up to down and down to up still needs the application of an external magnetic field unless the symmetry of the system is broken. This renders such switching scheme not very useful for real memory devices. In the third part of the thesis, we show through micromagnetic simulations that if the magnet has a wedge shape, the symmetry of the system is broken and the magnet can be deterministically switched from up to down and down to up even in the absence of an external magnetic field. Our simulations are supported by recent experiments, performed in our group. In the last part, we show how a bilayer of two heavy metals (Ta and Pt) can be used to increase the spin orbit torque efficiency. Interfaces of ferromagnet with Ta and that of ferromagnet with Pt exhibit spin orbit torques in opposite directions, so it is expected that their effects will cancel. Instead, in our experiments we find that the spin orbit torque efficiency at the Ta/CoFeB interface increases if a Pt layer exists under the Ta layer. Modeling of the system based on conventional spin transport physics cannot explain this result.
Spin Transfer Torque Based Devices Circuits And Memory
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Author : Brajesh Kumar Kaushik
language : en
Publisher: Artech House
Release Date : 2016-10-31
Spin Transfer Torque Based Devices Circuits And Memory written by Brajesh Kumar Kaushik and has been published by Artech House this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-10-31 with Technology & Engineering categories.
This first-of-its-kind resource is completely dedicated to spin transfer torque (STT) based devices, circuits, and memory. A wide range of topics including, STT MRAMs, MTJ based logic circuits, simulation and modeling strategies, fabrication of MTJ CMOS circuits, non-volatile computing with STT MRAMs, all spin logic, and spin information processing are explored. State-of-the-art modeling and simulation strategies of spin transfer torque based devices and circuits in a lucid manner are covered. Professional engineers find practical guidance in the development of micro-magnetic models of spin-torque based devices in object-oriented micro-magnetic framework (OOMMF) and compact modeling of STT based magnetic tunnel junctions in Verilog-A. The performance parameters and design aspects of STT MRAMs and MTJ based hybrid spintronic CMOS circuits are covered and case studies are presented demonstrating STT-MRAM design and simulation with a detailed analysis of results. The fundamental physics of STT based devices are presented with an emphasis on new advancements from recent years. Advanced topics are also explored including, micromagnetic simulations, multi-level STT MRAMs, giant spin Hall Effect (GSHE) based MRAMs, non-volatile computing, all spin logic and all spin information processing.
Spin Torque Effects In Mgo Based Magnetic Tunnel Junctions
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Author : Hsin-wei Tseng
language : en
Publisher:
Release Date : 2013
Spin Torque Effects In Mgo Based Magnetic Tunnel Junctions written by Hsin-wei Tseng and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
This thesis work focuses on understanding the fundamentals of the spintorque effect in MgO-based high tunneling magnetoresistance (TMR) magnetic tunnel junction (MTJ) nanopillar geometry devices. In order to achieve this goal, I have successfully established a reliable and repeatable high TMR and low resistance-area (RA) product MgO sputtering process at Cornell. Currently, we are capable of sputtering TMR (>100% with RA
Interfacial Effects In Fecob Based Magnetic Tunnel Junctions And Spin Hall Effect Bi Layer Structures
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Author : Yun Li
language : en
Publisher:
Release Date : 2014
Interfacial Effects In Fecob Based Magnetic Tunnel Junctions And Spin Hall Effect Bi Layer Structures written by Yun Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
The transfer of spin angular momentum from a spin-polarized current to a ferromagnet can generate sufficient torque to reorient the magnet's moment, thus this effect has prospective applications in spintronics. In this dissertation, the main theme of my work has been the study of spin-transfer-driven ferromagnetic resonance (STFMR) signals to understand what is the interfacial effects on the spin transfer torque (STT) in magnetic tunnel junction (MTJ) devices with a nanopillar geometry and bilayer spin Hall effect structures. In the first part of my work, I have studied the bias dependence of the spin transfer torques in the as-grown and annealed FeCoB/MgO/FeCoB MTJs by ST-FMR measurement. The motivation of this work was to understand the important mechanisms contributing to the in-plane torque with a view to optimizing the switching current of devices. I have found the annealing reduces the inelastic tunneling component of the junction conductance, and creates or enhances a peak at about 0.15V above the Fermi level in the density of states of the minority band of the electrodes, which may be the reason for the asymmetry of the bias dependence of the in-plane torque. This peak location is essentially the same as the peak of the minority band states that has previously observed on the surface of bcc (100) Fe. The existence of these interfacial states can also explain the asymmetry of the TMR, and the bias dependence of both G AP and GP . As a function of temperature, my experimental STTs can be explained by magnon contributions. My results show that with a relative increase of 50% in tunneling MR, however, both in-plane torque and perpendicular torque have been depressed at low temperature, indicating that magnon assisted tunneling, which results in a spin-flip process for the tunneling electron, has a negative contribution to the spin polarization, but plays a positive role in STT, with the latter consistent with recent theoretical predictions. In the second part of my work, I have studied the spin-torque effects on the FeCoB/W bi-layer structures with different W phases. The motivation of this work was to investigate the spin Hall and spin pumping effects in this system. I have observed a greatly enhanced magnetic damping coefficient for the Fe40Co40B20 layer with [alpha]-W, and I tentatively attribute these results to a significantly enhanced spin pumping effect in [alpha]-W, relative to that in [beta]-W. Magnetization measurements indicate that the two different types of Fe40Co40B20/W bilayers also have substantially different interfacial magnetic anisotropy coefficients.
Characterization Of Magnetic Tunnel Junctions For Spin Transfer Torque Magnetic Random Access Memory
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Author : Joshua Dill
language : en
Publisher:
Release Date : 2014
Characterization Of Magnetic Tunnel Junctions For Spin Transfer Torque Magnetic Random Access Memory written by Joshua Dill and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
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.
Mastering The Influence Of Thermal Fluctuations On The Magnetization Switching Dynamics Of Spintronic Devices
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Author : Bertrand Lacoste
language : en
Publisher:
Release Date : 2013
Mastering The Influence Of Thermal Fluctuations On The Magnetization Switching Dynamics Of Spintronic Devices written by Bertrand Lacoste and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Spin-transfer torque magnetic random-access memory (STTRAM) are very promising non-volatile and enduring memories to replace charged-based RAM. However, in conventional in-plane or out-of-plane STTRAM technologies, the switching time is limited to about 10~ns because the reversal process is stochastic i.e. it is triggered by thermal fluctuations. In order to render the reversal deterministic and faster, an approach consists in adding to the magnetic tunnel junction (MTJ) stack another spin-polarizing layer whose magnetization is orthogonal to that of the MTJ reference layer. We particularly investigated the case where a perpendicular polarizer is added to an in-plane magnetized tunnel junction. The STT from the perpendicular polarizer initiates the reversal, but it also creates oscillations of the resistance between its two extremal values. This behavior is usually interesting to realize STT nano-oscillators (STO). In this thesis, the dynamics of the system comprising an in-plane free layer, an in-plane reference layer and a perpendicular polarizer is studied both experimentally and theoretically (analytically and by simulations) in the framework of the macrospin approximation. For a single layer free layer oscillating due to the STT of the perpendicular polarizer, an accurate description of the oscillations is presented, in which the anisotropy field, the applied field and the in-plane STT are treated as perturbations. In the particular case of a synthetic ferrimagnetic (SyF) free layer, analytical expressions of the critical currents and of the oscillations equation of motion are computed and compared to simulations. These results are used to determine the phase diagram of the complete system. The in-plane anisotropy field is found to play a dramatic role, which is confirmed by experimental data from real-time measurements on MgO-based nano-pillars. It is shown that the cell aspect ratio can be used to tune the relative influence of the STT from the in-plane reference layer and from the out-of-plane polarizer. This allows achieving well controlled sub-nanosecond switching in STTRAM.