Next Generation Spin Torque Memories

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Next Generation Spin Torque Memories

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Author : Brajesh Kumar Kaushik
language : en
Publisher: Springer
Release Date : 2017-04-07

Next Generation Spin Torque Memories written by Brajesh Kumar Kaushik and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-04-07 with Technology & Engineering categories.

This book offers detailed insights into spin transfer torque (STT) based devices, circuits and memories. Starting with the basic concepts and device physics, it then addresses advanced STT applications and discusses the outlook for this cutting-edge technology. It also describes the architectures, performance parameters, fabrication, and the prospects of STT based devices. Further, moving from the device to the system perspective it presents a non-volatile computing architecture composed of STT based magneto-resistive and all-spin logic devices and demonstrates that efficient STT based magneto-resistive and all-spin logic devices can turn the dream of instant on/off non-volatile computing into reality.

Spintronics

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Author : Terunobu Miyazaki
language : en
Publisher:
Release Date : 2007

Spintronics written by Terunobu Miyazaki and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.

Towards High Density Low Power Spin Transfer Torque Random Access Memory

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Author : Urmimala Roy
language : en
Publisher:
Release Date : 2015

Towards High Density Low Power Spin Transfer Torque Random Access Memory written by Urmimala Roy 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.

In this work, we investigate the prospects for spin-transfer-torque random access memory (STTRAM) as the new generation low-power high-density non-volatile memory. Possible means to lower the switching current and increase the packing density of STTRAM are proposed. In an STTRAM cell, the logical value of the memory bit is stored as orientation of magnetic moment in its ferromagnetic ``free'' layer. The bit typically consists of two thin film ferromagnets (FM) separated by an insulating tunnel barrier as in a magnetic tunnel junction (MTJ) structure. One of the two FM layers has fixed magnetization direction, while the other layer is free to be switched. We first study STT-assisted switching in spin valve structures with in-plane, perpendicular, and canted magnetizations in free and (or) reference layers using point contact measurements to explore the use of non-collinear magnetizations in free and fixed FM to reduce both switching current and time. Next, we consider the possibility of storing two memory bits within a single MTJ with a cross-shaped free layer that could still be addressed by one selection transistor. We provide a detailed discussion of the switching dynamics and associated regions of reliable switching currents, in addition to illustrating the effects of varying device geometry on the latter. Moving on from the standard MTJ structure, we then consider the possible use of topological insulators, as opposed to the fixed FM, as the spin-polarizer layer. It has been established that spin and momentum are locked helically in the surface states of a three-dimensional topological insulator (TI). Suggestions of possible use of the TI spin-polarized surface states in spintronic devices to induce reversal of a magnet have been made using theoretical and experimental studies. Here, we simulate magnetization reversal of a metallic nanomagnet by an underlying TI. The TI, thanks to the spin-momentum helical locking of the surface states, causes a spin-polarized current injection to the FM above it. We study the efficiency of the spin injection as a function of varying transparency of the TI-FM interface. The transport in the TI and the FM is assumed to be diffusive at room temperature for the assumed resistance values. Finally, we take into account random thermal fluctuations leading to write error rate (WER) in STTRAM write operation and use Fokker-Planck method and stochastic Landau-Lifshitz-Gilbert-Slonczewski equation to model WER in STTRAM. We conclude with possible future research directions.

Spin Transfer Torque Based Devices Circuits And Memory

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Author : Brajesh Kumar Kaushik
language : en
Publisher: MICROTECHNOLOGY NANOTECHNOLOGY
Release Date : 2016

Spin Transfer Torque Based Devices Circuits And Memory written by Brajesh Kumar Kaushik and has been published by MICROTECHNOLOGY NANOTECHNOLOGY this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Spintronics 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.

Spintronics Based Computing

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Author : Weisheng Zhao
language : en
Publisher: Springer
Release Date : 2015-05-11

Spintronics Based Computing written by Weisheng Zhao and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-05-11 with Technology & Engineering categories.

This book provides a comprehensive introduction to spintronics-based computing for the next generation of ultra-low power/highly reliable logic. It will cover aspects from device to system-level, including magnetic memory cells, device modeling, hybrid circuit structure, design methodology, CAD tools, and technological integration methods. This book is accessible to a variety of readers and little or no background in magnetism and spin electronics are required to understand its content. The multidisciplinary team of expert authors from circuits, devices, computer architecture, CAD and system design reveal to readers the potential of spintronics nanodevices to reduce power consumption, improve reliability and enable new functionality.

Non Volatile Memories

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Author : Pierre-Camille Lacaze
language : en
Publisher: John Wiley & Sons
Release Date : 2014-12-01

Non Volatile Memories written by Pierre-Camille Lacaze 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 2014-12-01 with Technology & Engineering categories.

Written for scientists, researchers, and engineers, Non-volatile Memories describes the recent research and implementations in relation to the design of a new generation of non-volatile electronic memories. The objective is to replace existing memories (DRAM, SRAM, EEPROM, Flash, etc.) with a universal memory model likely to reach better performances than the current types of memory: extremely high commutation speeds, high implantation densities and retention time of information of about ten years.

Spin Torque Transfer Logic And Memory Design

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Author : Sridevi Srinivasan Lakshmipuram
language : en
Publisher:
Release Date : 2014

Spin Torque Transfer Logic And Memory Design written by Sridevi Srinivasan Lakshmipuram and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Magnetic memory (Computers) categories.

The Spin Hall Effect Induced Spin Transfer Torque In Magnetic Heterostructures

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Author : Chi-Feng Pai
language : en
Publisher:
Release Date : 2015

The Spin Hall Effect Induced Spin Transfer Torque In Magnetic Heterostructures written by Chi-Feng Pai 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.

The spin Hall effect (SHE) induced spin current in some certain heavy transition metals has been shown to impose spin transfer torque (STT) upon an adjacent magnetic layer strong enough to excite magnetization switching and/or magnetic oscillation therein. The similarities and differences between this new paradigm and the traditional route of spin generation will be the main focus of this dissertation. Firstly, these phenomena stemming from the SHE can be viewed as a reminiscent of the traditional spin-torque generation from a ferromagnetic layer in spin-valve-like devices, except that now the source of the STT is coming from the normal metal (NM) layer instead of the ferromagnetic (FM) spin-polarizer in those traditional devices with sandwich structures (FM/NM/FM or FM/Insulator/FM). In this fashion, essentially only one layer of ferromagnetic layer is required as the read-out means. In the first part of this dissertation, I will show that this detection of the spin-Hall response can be done either via anisotropic magnetoresistance (AMR), anomalous Hall effect (AHE), or planar Hall effect (PHE) in a simple NM/FM bilayer structure. By analyzing the data from both high and low frequency measurements, the spin Hall angle, which represents the strength of the SHE, from various transition metals are estimated. Secondly, the symmetry of the SHE, from which the resulting spin current is transverse to the applied charge current, allows us to design STT devices using in-plane charge current (CIP) instead of the traditional utilization of current-perpendicular-toplane (CPP) architecture. This facilitates the realization of a new three-terminal device, which eventually leads us to a prototype of magnetic cross-point nonvolatile memory. By studying the SHE-STT switching from beta-Ta and beta-W-based three-terminal devices, I will confirm that the spin Hall angle of [beta]-Ta and [beta]-W are respectively [ALMOST EQUAL TO]-0.15 and [ALMOST EQUAL TO]-0.30, which are consistent with the results from the first part of this work. The strong SHE from these transition metals can also be adopted to modulate spin-waves and will be shown at the end of this section. Lastly, the adaptation of a CIP architecture means that the spin-charge transport properties in the spin Hall devices are, per se, more complicated than that in their CPP counterparts. The interface(s) as well as the bulk properties in these magnetic heterostructures both play important roles in determining the final spin transport properties, thereby the effective spin Hall efficiency. In this final section, I will present the variation of the current induced damping-like torque and field-like torque in NM/(spacer)/FM heterostructures, from which the possible interplay between interface(s) and bulk, as well as their relative contributions, can be estimated.

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.

Next Generation Mram Development

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Author : Masood Qazi
language : en
Publisher: LAP Lambert Academic Publishing
Release Date : 2010-04

Next Generation Mram Development written by Masood Qazi and has been published by LAP Lambert Academic Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010-04 with categories.

Only recently has the possibility of a universal memory, a fast random access memory that retains its state during complete power-down, turned into a realizable opportunity. Such a memory can eliminate static power, improve system reliability in the face of power interruption, and eliminate the need for a separate FLASH memory module, reducing system component count. One candidate in the race for a universal memory is magnetoresistive random access memory (MRAM). In the development of MRAM, design challenges related to isolating memory elements, obtaining a compatible operating point with CMOS technology, and sensing data reliably have emerged. Therefore, there still exists a barrier to achieving the cost and performance characteristics of traditional volatile solid state memories---SRAM and DRAM. In this work, a 4kb MRAM array is designed to evaluate the feasibility of a promising new form of MRAM based on the phenomenon of spin torque transfer switching. The design of the test site and measurement setup is discussed, showing how to explore a multidimensional parameter space of operating conditions to obtain a viable design point for the next generation of MRAM technology.