Spin-transfer torque in magnetic tunnel junctions: Scattering theory

Jiang Xiao, Gerrit E.W. Bauer, Arne Brataas

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91 Citations (Scopus)


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.

Original languageEnglish
Article number224419
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number22
Publication statusPublished - 2008 Jun 12


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