Mechanism and assessment of spin transfer torque stt based memory by iong ying loh b. R have the same sign, the nonequilibrium spin accumulation due to the rashbasplit 2deg and that due to the helical dirac state are opposite. Spintransfertorque magnetoresistive randomaccess memory sttmram is an emerging nonvolatile memory that uses magnetic tunnel junctions mtjs to store information. We find that the strength of the torque per unit charge current density in the bi 2se 3 is greater than for any other spin. It is understood that the origin of spin torque is the interaction of spinpolarized conducting electrons with localized magnetic moments 6. View spin transfer torque research papers on academia. Impact of spinorbit torque on spintransfer torque switching in. Based on the sign of the torque we measure experimentally, we can identify the topological surface state as the dominant source for the generation of torque in our experiments. Spinorbit torques arise from the spin hall effect creating a spincurrent, which then provides a spintransfer torque that acts on the magnetization of a ferromagnet. Spin transfer torque and spin orbit torque both happen when the nonequilibrium spin density the spin quantity carried by the electronic flux is not collinear to the direction of the magnetization.
Engineering of metallic multilayers and spin transfer torque devices. Spin torque oscillators spin transfer torque stt is a dissipative phenomenon in which a spinpolarized current transfers angular momentum to the local magnetization and directly impacts its magnetodynamics. One should look at different samplings to see if the results physical quantities of study obtained converge within some toleranceaccuracy. James allen uc santa barbara science technology spin torque transfer ram, sttram spin torque transfer nanooscillators a free powerpoint ppt presentation displayed as a flash slide show on id. Hence, the spin transfer effect provides a means of producing an agile, nanoscale, ghz radiation source that can be fabricated on a chip. In his paper, a five layers structure is considered. When summed over all fermi surface electrons, these processes reduce the transverse component of the transmitted and reflected spin currents to nearly zero for most systems of interest.
Ad and fl components stt on domain walls spin pumping sttinduced magnetization dynamics spinorbit coupling and spinorbit torques sot spin hall and rashba effects sot measurements threeterminal sot magnetic tunnel junctions. In this article, we extend the collinear theory of di usive transport for spindependent conduction to include spindependent thermoelectricity2225, spinorbit. However, delivering on this promise requires addressing two key design challenges. Depending on the details of the magnetic state, and of the sign of the spinpolarized current, stt can. Spintransfer torques occur in magnetic heterostructures because the transverse component of a spin current that flows from a nonmagnet into a ferromagnet is absorbed at the interface. Spintransfer torques in antiferromagnetic metals from first. This is the fundamental of the novel write mechanism in sttram, currentinduced magnetization switching. Spin transfer torque corresponds to the interaction of a spin polarized electronic current with the local magnetization. Spin transfer torque ram sttram, built using magnetic tunnel junctions mtjs, is a promising universal memory candidate. Devices consisting of topological insulators and ferromag.
As a result of theoretical predictions by slonczewski 2 and berger 3 in 1996 and early experimental verification 46 of spin transfer torques, there has been tremendous excitement driven by a number of factors. This technology allows a writing speed of a few nanoseconds, a density close to that of dram, combined with an intrinsic nonvolatility. This still neglects the movement of domain walls by stt as used in race track memory devices. Could you explain the mechanism of spin transfer torque and. Spin transfer torque devices utilizing the giant spin hall effect of tungsten applied physics letters 101, 122404 2012. Pdf introduction to spin transfer torque researchgate.
Mechanism and assessment of spin transfer torque stt. When an electron spin carried by the current interacts with a magnetic layer, the exchange interaction leads to torques between the spin and the magnetization. Key concepts in spin transport in fmnm systems interaction of a spin polarized current with a magnetic layer spin transfer torque stt. Approximate image storage with multilevel cell sttmram. Reliability analysis of spin transfer torque based look up tables under process variations and nbti aging ragh kuttappaa, houman homayoun b, hassan salmanic, hamid mahmoodia. An electric current is generally unpolarized consisting of 50% spinup and 50%. These nanoscale spin transfer oscillators can have frequencies ranging perhaps as high as 100 ghz, have demonstrated linewidths as narrow as 2 mhz, and the frequency can be tuned by adjusting the current. Depending on the details of the magnetic state, and. We predict an unconventional spintransfer torque stt acting on the magnetization of a free ferromagnetic f layer.
This is the introductory paper for a cluster of \current perspectives articles on spin transfer torques published in volume 320 of the journal of magnetism and magnetic. Spintransfer torque is an effect in which the orientation of a magnetic layer in a tunnel magnetoresistance or spin valve can be modified using a spinpolarized current. Ad and fl components stt on domain walls spin pumping sttinduced magnetization dynamics spin orbit coupling and spin orbit torques sot spin hall and rashba effects sot measurements. Spintransfer torques for domain walls in antiferromagnetically. Graphene is an ideal channel material in this context due to its long spin diffusion length, gatetunable. Atk implements a convenient analysis object for calculating the spin transfer torque using method 2 in the linearresponse approximation, where the non. I know that it is not the same thing as spintransfer torque. This interoperability is hardware proven on a xilinx virtex7 fpga and is now available for designs needing lowlatency, high memory throughput using mram technology. Pdf spintransfer torque in magnetic tunnel junctions. Robust synchronization of spintorque oscillators with an lcrload. Mtjs with a crystalline mgo001 tunnel barrier sandwiched between ferromagnetic layers, such as cofeb, exhibit giant tunnel magnetoresistance, which is used to readout the stt. What links here related changes upload file special pages permanent link page information wikidata item cite this page. Pdf spin transfer torque corresponds to the interaction of a spin polarized electronic current with the local magnetization. The physics behind these oscillations is based on the spin transfer torque force, with which a spin polarized electrical current acts on a free magnet.
We obtain a spin dependent seebeck coe cient for permalloy of 3. However, the main challenge remains to be the relatively high current and delay needed for the write operation 1. Therefore, to a good approximation, the torque on the magnetization is proportional to the transverse piece of the incoming spin current. Oct 18, 2017 spin transfer torque is an effect in which the orientation of a magnetic layer in a magnetic tunnel junction or spin valve can be modified using a spin polarized current. Spin transfer torque in a graphene lateral spin valve. Spin transfer torque is a promising new mechanism to write magnetic storage elements in magnetic random access memory mram devices with magnesium oxide mgobased magnetic tunnel junction mtj architecture. Spin transfer torque magnetic randomaccess memory sttram or sttmram is a nonvolatile memory with nearzero leakage power consumption which is a major advantage over chargebased memories such as sram and dram. Spintransfer torque stt is an effect in which the orientation of a magnetic layer in a magnetic. Spin orbit torque memory for nonvolatile microprocessor caches. They may be viewed from this source for any purpose, but reproduction or distribution in any format is. Graphene is an ideal channel material in this context due to its long spin diffusion. In the spinmagnetization coupling, the spin angular momentum is transferred to magnetization dynamics by a mechanism known as spintransfer torque stt.
The flow of spins is determined by the spin dependent transport properties, like conductivity, interface resistance, and spin flip scattering in the magnetic multilayer. Jul 23, 2014 charge flowing in a thin film of the topological insulator bismuth selenide at room temperature can lead to spin accumulation in the insulator and a resultant strong spin transfer torque on an. We demonstrate this fact explicitly using free electron models and first principles electronic structure calculations for real material interfaces. Spin transfer torques in antiferromagnetic metals from first principles yuan xu, shuai wang, and ke xia state key laboratory for surface physics, institute of physics, chinese academy of sciences, p. Spin torque oscillator sto is a nanoscale spintronic device generating periodic microwave in the frequency range of several ghz oscillations see ref. Cornell university 2012 this dissertation describes a number of research projects with the common. Materials for spintransfertorque magnetoresistive random. In particular, spintransfer torque mram sttmram composed of. This tutorial article is designed for beginning graduate students who are interested in the physics of spin transfer torques in magnetic devices. Introduction to spin torques and spinorbit torques in. Remarkable progress in stt switching with mgo mtjs and increasing interest in sttmram in semiconductor industry have been witnessed in recent years. A spin polarized current entering a ferromagnetic element thus may change the magnetization orientation of this element and by this information can be stored inside it. Pdf we present a theoretical study of the spintransfer torque vector and the tunneling magnetoresistance tmr for symmetric magnetic tunnel junctions.
Field and dampinglike spintransfer torque in magnetic. The papers most influential in launching the study of spin transfer torques came in 1996, when slonczewski and berger independently predicted that current flowing perpendicular to the plane in a metallic multilayer can generate a spin transfer torque strong enough to reorient the magnetization in one of the layers. Spin transfer torque zhangli model nmag provides support for the zhangli extension to the landaulifshitzgilbert llg equation, in order to model the interaction between a uniform electric current density and a spatially varying magnetisation. Delivering on the promise of universal memory for spin. Low energy spin transfer torque ram sttram spram zach foresta april 23, 2009. In this tutorial we teach you the basics to our torque system. Spin transfer torque occurs in situations where a current of spinpolarized carriers from the left part of a device with a particular polarization given by the unit vector enters the right part of the device with a different magnetization direction given by the unit vector. Introduction the primary application of stt has been in memory application sttram.
The term spintronics is a portmanteau of spin transportelectronics. Magnetic systems are promising candidates for next generation memory due to their intrinsic nonvolatility and low dissipation during switching 1. Although most applications use mgobased mtjs, it is very difficult to maintain a high breakdown voltage when the mgo thickness is less than 1 nm. Here we demonstrate nanocontactbased spin wave generation in magnetic tunnel junctions and observe largefrequency steps consistent with. Applied physics 2007 university of malaya submitted to the department of materials science and engineering. This tutorial article introduces the physics of spin transfer torques in magnetic devices.
Mechanism and assessment of spin transfer torque stt based memory. To explain, in contrast to electronic devices that. View spin transfer torque mram research papers on academia. The underlying effect, called spin transfer torque stt 6,7, has been studied intensively in several magnetization switching experiments using timeresolved stxm 8,9,10.
Spin orbit torque memory for nonvolatile microprocessor. Mar 27, 2018 datasheet for mr4a16b, 16 mb, parallel io mram. Spin transfer torque generated magnetic droplet solitons. Spintorque generation in topological insulator based. Spin transfer technologies new psc structure shows a lot of promise to solve a number of those issues and pave the path for mram to take a significant share of the embedded memory market. The torque arises because a polarized electron in a nonmagnet feels a large exchange. Device implications of spintransfer torques sciencedirect. Everspin builds ecosystem for 1gigabit spintransfer. Spinbased devices are widely discussed for postcomplementary metaloxidesemiconductor cmos applications. Lateral spin transfer torque induced magnetic switching at. Highly efficient inline magnetic domain wall injector. Could you explain the mechanism of spin transfer torque. The result is an expression for the torque in terms of the geometry of the devices and the magnetic configuration.
In addition, multilevel cell spintransfer torque mram sttmram offers unique design opportunities as the image memory. Dynamic single and dual rail spin transfer torque look up. Mram, the worlds leading developer and manufacturer of magnetoresistive ram mram. Characterization of spin transfer torque and magnetization manipulation in magnetic nanostructures chen wang, ph. We demonstrate a highly efficient and simple scheme for injecting domain walls into magnetic nanowires. Oct 15, 20 spinbased devices are widely discussed for postcomplementary metaloxidesemiconductor cmos applications. Spin transfer torqueram devices as a future nonvolatile. Reliability analysis of spin transfer torque based look up. For at least two distinct reasons, this interaction induces a transfer of spin angular mo.
Everspin expands spintransfer torque mram ecosystem support for its 1 gigabit sttmram with cadence design ip and verification ip the everspin team continues to build strong market support for our groundbreaking 1 gb sttmram devices, as we march toward full production of this product, said kevin conley, president and ceo of everspin. Our intention is to be accessible to beginning graduate students. As a result of theoretical predictions by slonczewski 2 and berger 3 in 1996 and early experimental verification 46 of spin transfer torques, there has been tremendous excitement driven. Low writing energy and sub nanosecond spin torque transfer switching of inplane magnetic tunnel junction for spin torque transfer random access.
Deciding on kpoint sampling is always a matter of convergence with respect to the kpoint density. Everspin and phison partner to bring spintransfer torque mram to next generation enterprise ssd controllers chandler, az july 24, 2019 everspin technologies, inc. When a sufficient current density passes through the mtj, the spinpolarized current will exert a spin transfer torque to switch the magnetization of the free layer. Our intention is that it be accessible to beginning graduate students. The goal of these articles is to provide an introduction to the topical scienti c issues concerning the theories, experiments, and commercial applications related to spin transfer torques. Sttram offers a cmos compatible and nonvolatile memory and hence a zero leakage alternative to sram.
Everspin builds ecosystem for 1gigabit spintransfer torque. Spintransfer torque generated by a topological insulator. Pdf spintransfer torque and dynamics jacques miltat. When the electrons incoming from the left side enter the right magnetic part, they. In this article, we extend the collinear theory of di usive transport for spindependent conduction to include spindependent thermoelectricity2225, spinorbit e ects8,26,27 and spindependent thermal transport28. Oct 21, 2006 the flow of spins is determined by the spin dependent transport properties, like conductivity, interface resistance, and spin flip scattering in the magnetic multilayer. Spintransfer torque generated by a topological insulator article in nature 5117510. In this article, we extend the collinear theory of di usive transport for spin dependent conduction to include spin dependent thermoelectricity2225, spin orbit. Perpendicular spin transfer torque magnetic random access memories with high spin torque efficiency and thermal stability for embedded applications invited journal of applied physics 115, 172615 2014. A multiscale picture a powerful driving force behind the development of fast, high density, nonvolatile memory technology. Emerging applications, especially those using batteries, such as arvr, iot and many machine learning. Introduction to spin torques and spinorbit torques in metal.
A number of spin device ideas propose using spin current to carry information coherently through a spin channel and transfering it to an output magnet by spin transfer torque. Spin transfer torque can be used to flip the active elements in magnetic randomaccess memory. Cataloged from student submitted pdf version of thesis. Spintransfer torque stt is an effect in which the orientation of a magnetic layer in a magnetic tunnel junction or spin valve can be modified using a spinpolarized current charge carriers such as electrons have a property known as spin which is a small quantity of angular momentum intrinsic to the carrier. Spintransfer torque stt switching demonstrated in submicron sized magnetic tunnel junctions mtjs has stimulated considerable interest for developments of stt switched magnetic random access memory sttmram. Preventing design reverse engineering with reconfigurable. Spin transfer torque stt technology 2, which relies on the use of a spin polarized current applied through the mtj to switch the magnetic state. Everspin and phison partner to bring spintransfer torque.
Spin transfer torque driven higherorder propagating spin waves in. This will help you understand flipping and spinning. Everspin and northwest logic have just announced full interoperability between northwest logics mram controller core and everspin technologies stmram spintorque magnetic ram chips. Magnetic moment is transferred from the conduction electrons to the. Grandis press release describing partnership with hynix pdf.