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Efficiency of Spin-Transfer-Torque Switching and Thermal-Stability Factor in a Spin-Valve Nanopillar with First- and Second-Order Uniaxial Magnetic Anisotropies

Rie Matsumoto1, Hiroko Arai2,1, Shinji Yuasa1, and Hiroshi Imamura1,*

  • 1National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan
  • 2PRESTO, JST, Honcho, Kawaguchi, Saitama 332-0012, Japan

  • *h-imamura@aist.go.jp
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Phys. Rev. Applied 7, 044005 – Published 7 April, 2017

DOI: https://doi.org/10.1103/PhysRevApplied.7.044005

Abstract

The efficiency of spin-transfer-torque (STT) switching and the thermal-stability factor are important figures of merit in STT-based magnetoresistive random-access memory. We derive analytical expressions of the STT-switching efficiency and the thermal-stability factor for a perpendicularly magnetized spin-valve nanopillar with the first- and the second-order uniaxial magnetic anisotropy. It is shown that the STT-switching efficiency is maximized when the effective first-order anisotropy constant (Ku1,eff) is equal to the second-order anisotropy constant (Ku2). It is also shown that the thermal-stability factor is most (least) sensitive to a variation of the applied current when Ku2=−0.41 (0.70) Ku1,eff.

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Phys. Rev. Applied 7, 044005– Published 7 April, 2017
  • Received 2 December 2016

© 2017 American Physical Society

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