Spin-transfer torque in magnetic tunnel junctions: Scattering theory

Jiang Xiao, Gerrit E. W. Bauer, and Arne Brataas
Phys. Rev. B 77, 224419 – Published 12 June 2008

Abstract

We study the bias-dependent spin-transfer torque in magnetic tunnel junctions in the Stoner model by scattering theory. We show that the in-plane (Slonczewski type) torque vanishes and subsequently reverses its direction when the bias voltage becomes larger or the barrier wider than material and device-dependent critical values. We are able to reproduce the magnitude and the bias dependence of measured in-plane and out-of-plane torques using realistic parameters. The condition for the vanishing torque is summarized by a phase diagram depending on the applied bias and barrier width, which is explained in terms of an interface spin polarization and the electron focusing by the barrier. Quantum size effects in the spin-transfer torque are predicted as a function of the thickness of a normal-metal layer inserted between the ferromagnet and tunnel barrier.

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  • Received 29 March 2008

DOI:https://doi.org/10.1103/PhysRevB.77.224419

©2008 American Physical Society

Authors & Affiliations

Jiang Xiao and Gerrit E. W. Bauer

  • Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands

Arne Brataas

  • Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway

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Issue

Vol. 77, Iss. 22 — 1 June 2008

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