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Theory of spin-transfer torque in the current-in-plane geometries

Wessely, O.; Umerski, A. and Mathon, J. (2009). Theory of spin-transfer torque in the current-in-plane geometries. Physical Review B, 80(1) 014419-1.

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DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1103/PhysRevB.80.014419
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Abstract

Two alternative current-induced switching geometries, in which the current flows parallel to the magnet/nonmagnet interface, are investigated theoretically using the nonequilibrium Keldysh theory. In the first geometry, the current is perpendicular to the polarizing magnet/nonmagnet interface but parallel to the nonmagnet/switching magnet interface (CPIP). In the second geometry, the current is parallel to both polarizing magnet/nonmagnet and nonmagnet/switching magnet interfaces (CIP). Calculations for a single-orbital tight-binding model indicate that the spin current flowing parallel to the switching magnet/nonmagnet interface can be absorbed by a lateral switching magnet as efficiently as in the traditional current-perpendicular-to-plane (CPP) geometry. The results of the model calculations are shown to be valid also for experimentally relevant Co/Cu CPIP system described by fully realistic tight-binding bands fitted to an ab initio band structure. It is shown that almost complete absorption of the incident spin current by a lateral switching magnet occurs when the lateral dimensions of the switching magnet are of the order of 50–100 interatomic distances, i.e., about 20 nm and its height as small as a few atomic planes. It is also demonstrated that strong spin current absorption in the CPIP/CIP geometry is not spoiled by the presence of a rough interface between the switching magnet and nonmagnetic spacer. Polarization achieved using a lateral magnet in the CIP geometry is found to be about 25% of that in the traditional CPP geometry. The present CPIP calculations of the spin-transfer torque are also relevant to the so-called pure-spin-current-induced magnetization switching that had been recently observed.

Item Type: Journal Article
Copyright Holders: 2009 The American Physical Society
ISSN: 1098-0121
Project Funding Details:
Funded Project NameProject IDFunding Body
Not SetNot SetUK Engineering and Physical Sciences Research Council
Keywords: interface magnetism; magnetic switching; spin polarised transport; tight-binding calculations
Academic Unit/Department: Mathematics, Computing and Technology > Mathematics and Statistics
Item ID: 18022
Depositing User: Andrey Umerski
Date Deposited: 27 Aug 2009 13:28
Last Modified: 12 Dec 2012 19:45
URI: http://oro.open.ac.uk/id/eprint/18022
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