It is particularly interesting for high speed applications that do not require very high density because of two transistors per bit cell. Key concepts in spin transport in fmnm systems interaction of a spin polarized current with a magnetic layer spin transfer torque stt. Spin transfer torquethe transfer of angular momentum from a spinpolarized current to a ferromagnets magnetizationhas already found commercial application in memory devices, but the. 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. 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. Spin transfer torque induced domain wall oscillations in. We predict an unconventional spintransfer torque stt acting on the magnetization of a free ferromagnetic f layer. Spin transfer torque induced switching in magnetic tunnel.
Impact of spinorbit torque on spintransfer torque switching in magnetic tunnel junctions skip to main content thank you for visiting. It has been predicted that a processors caches could occupy as much as 90% of chip area a few technology nodes from the current ones. We resolve conflicting estimates for the order of magnitude of the spin transfer torque by firstprinciples calculations. Our intention is to be accessible to beginning graduate students. 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. An electric current is generally unpolarized consisting of 50% spinup and 50%. Design of an erasable spintronics memory based on current. Spin transfer torque induced domain wall oscillations in ferromagnetic nanowire with a nanoscale dzyaloshinskiimoriya interaction region. Our intention is that it be accessible to beginning graduate students. Spin transfer torque devices utilizing the giant spin hall. The university of texas at austin, 2011 supervisor. Characterization of magnetic tunnel junctions for spin transfer torque magnetic random access.
This thesis describes experimental studies of the spin transfer torque induced switching in magnetic tunnel junctions mtj for the application of spin transfer torque random access memory sttram. Recent experimental and theoretical studies focus on spinmediated heat currents at interfaces between normal metals and magnetic insulators. Spin transfer torque induced oscillation and switching in. Pdf we present a theoretical study of the spintransfer torque vector and the tunneling magnetoresistance tmr for symmetric. Xiaobin wang and yiming huai avalanche technology, usa no access materials, devices and spin transfer torque in antiferromagnetic spintronics. Spintransfer torque and spinpolarization in topologicalinsulator. Spin transfer 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. Spintransfer torque magnetoresistive random access memory sttmram is a persistent memory technology that delivers performance, persistence, and durability utilizing variants of industry standard interfaces. Mechanism and assessment of spin transfer torque stt.
Remarkable progress in stt switching with mgo mtjs and increasing interest in sttmram in semiconductor industry have been witnessed in recent years. The former examines how reliably an applied spintransfer torque can excite magnetization dynamics that lead to a reversal of magnetization direction while the latter studies steady state dynamics provided by an oscillating spintransfer torque. Spintransfer torque switching at ultra low current densities. One of the most promising candidates for nvram technology is the spin transfer torque ram spram based on magnetic tunnel junction mtj device technology. 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. Lateral spin transfer torque induced magnetic switching at room.
At the end of the chapter 3 we simulate the magnetization dynamics under stt effect using the fastmag micromagnetic simulation software coupled. This is the fundamental of the novel write mechanism in sttram, currentinduced magnetization switching. We expose the theory of quantized spinpolarized electron transport perpendicular to the plane of a magnetic multilayer with noncollinear magnetization vectors. Cornell university 2012 this dissertation describes a number of research projects with the common. Current highspeed highdensity logic circuits like fpgascplas typically do not employ sttram or other sttbased elements. Spintransfer torque or spintorque, or stt based magnetic tunnel junction mtj is at the heart of a new generation of magnetismbased solidstate memory, the socalled spintransfertorque magnetic random access memory, or sttmram. Pdf spintransfer torque in magnetic tunnel junctions. Spintransfer torque magnetic memory sttmram is currently under. Spin transfer torque on magnetic insulators iopscience. This tutorial article introduces the physics of spin transfer torques in magnetic devices. Spinorbit torquedriven propagating spin waves science. Pdf spintransfer torque magnetic memory as a stochastic. Characterization of magnetic tunnel junctions for spin.
Spintransfer torque magnetic random access memory stt. 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. The term spintronics is a portmanteau of spintransportelectronics. Experimental observation of the optical spin transfer torque. We demonstrate this fact explicitly using free electron models and first principles electronic. Magnetic systems are promising candidates for next generation memory due to their intrinsic nonvolatility and low dissipation during switching 1. Emerging nonvolatile memories promise to replace sram and dram for overcoming the above bottleneck. In his paper, a five layers structure is considered. Among them, spin transfer torque magnetic ram sttmram is one of the most promising candidates for constructing the nextgeneration lowpower and highdensity nonvolatile memory.
We explore a 3d crosspoint spin transfer torque magnetic random access memory sttmram array based on the integration of a perpendicular magnetic tunneling junction pmtj with a matching twote. Spintransfer torque or spintorque, or stt based magnetic. Impact of spinorbit torque on spintransfer torque switching in. Spin transfer torque induced switching of nano magnets in lateral spin valve geometry at roomtemperature. Spintransfer torque switched magnetic tunnel junctions in. Applied physics 2007 university of malaya submitted to the department of materials science and engineering.
Est02880 magnetic immunity for everspin mram 073115. Delivering on the promise of universal memory for spintransfer torque ram sttram 1anurag nigam, 2clinton w. Us9577641b2 spin transfer torque based memory elements. Mechanism and assessment of spin transfer torque stt based memory by iong ying loh b. Spintransfer torques for domain walls in antiferromagnetically. Maxim tsoi in the scope of this thesis spin transfer torque stt driven switching and resonances in point contact experiments are investigated. Smullen, iv, 2vidyabhushan mohan, 3eugene chen, 2sudhanva gurumurthi, and 1mircea r. In this article, we investigate the use of multilevel spintransfer torque ram sttram cells in the design of processor caches. Nonvolatile ram nvram enables instantonoff computing, which drastically reduces power consumption.
The currents in magnetic multilayers are spin polarized and can carry enough angular momentum that they can cause magnetic reversal and induce stable precession of. However, the typical current densities required to create observable spin transfer torques in presentday studies exceed 10 11 a m. The recent emergence of spinorbit torque sot from pure spin currents has opened an additional avenue for the controlled manipulation of magnetic moments in spintronic devices, resulting in markedly improved efficiency and much lower power dissipation compared to conventional spin. The result is an expression for the torque in terms of the geometry of the devices and the magnetic configuration. This additional spin transfer torque can generate oscillatory magnetic modes or even magnetization reversal, for a sufficiently large current. Spin transfer torque random access memory sttram is a type of nonvolatile rams that is typically used for more conventional memory circuits, such as, cache, secondary storage etc. Magnetic switching and magnetodynamics driven by spin transfer torque by heidi seinige, m. Introduction to spin torques and spinorbit torques in. Pdf spin transfer torque corresponds to the interaction of a spin polarized electronic current with the local. Characterization of spin transfer torque and magnetization manipulation in magnetic nanostructures chen wang, ph. The flow of spins is determined by the spindependent transport properties, like conductivity, interface resistance, and spinflip scattering in the magnetic multilayer. Cu to cofe interface between the pillar and the lead causes spin accumulation in the pillar, which may then be used to set the magnetic orientation of the pillar by means of spin transfer torque.
Transfer torque, and spin hall effect in presence of an electromagnetic non. The dependence of resistance and currentdriven torque on relative angle between 2 magnetic moments of a multilayer pillar are derived. If you previously purchased this article, log in to readcube. Spin orbit torque magnetic ram sotmram approach represents a new way to overcome over spin transfer torque stt memory limitations by separating the reading and the writing paths. Onchip caches built on multilevel spintransfer torque. Magnetic switching and magnetodynamics driven by spin. Spin transfer torqueram devices as a future nonvolatile. Spin transfer torque devices utilizing the giant spin hall effect of tungsten appl. High density sotmram memory array based on a single. Spintransfer 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 spinpolarized current. Spin transfer torque stt induced magnetization switching and oscillation in nanometer scale magnetoresistance mr devices have been studied intensively due to its direct application in the nonvolatile stt random access memory sttram and its potential application in the high frequency spin torque oscillatior sto. Spin transfer torque induced switching of nano magnets in. A multiscale picture a powerful driving force behind the development of fast, high density, nonvolatile memory technology. Spintransfer torque magnetic memory as a stochastic memristive synapse for neuromorphic systems.
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