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Coresonant Enhancement of Spin-Torque Critical Currents in Spin Valves with a Synthetic-Ferrimagnet Free Layer

Neil Smith, Stefan Maat, Matthew J. Carey, and Jeffrey R. Childress
Phys. Rev. Lett. 101, 247205 – Published 11 December 2008
Physics logo See Synopsis: Putting a damper on the spin-torque effect

Abstract

It is experimentally shown that the critical current for onset of spin torque instability in current-perpendicular-to-plane spin valves can be strongly increased using “synthetic-ferrimagnet” free layers of form FM1/Ru/FM2 (FM=ferrromagnet). However, this increase occurs for only one polarity of bias current. A two-macrospin model is shown to reproduce the observations. The model suggests that this phenomenon is related to a polarity-dependent, spin torque-induced coresonance between the two natural dynamic modes of the FM1/FM2 couple. The coresonance condition facilitates energy transfer out of the spin-torque destabilized mode into the other stable mode whose effective damping (or line width) is strongly enhanced by spin torques.

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  • Received 14 July 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.247205

©2008 American Physical Society

Synopsis

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Putting a damper on the spin-torque effect

Published 11 December 2008

The effects of torques caused by spin-polarized currents are often unwanted in magnetic nanostructures, but they can be diminished with the right design.

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Authors & Affiliations

Neil Smith, Stefan Maat, Matthew J. Carey, and Jeffrey R. Childress

  • San Jose Research Center, Hitachi Global Storage Technologies, San Jose, California 95135, USA

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Issue

Vol. 101, Iss. 24 — 12 December 2008

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