Bias dependent oscillations in spin polarized tunneling

ORAL

Abstract

We investigated the bias dependence of spin polarized tunnelling in (pinned)CoFeB/ MgO/(free)CoFeB and (pinned)CoFeB/MgO/(free)NiFe tunnel junctions as a function of temperature and applied field angle. The differential magnetoresistance (MR) exhibits oscillations about zero MR when the free layer of the asymmetric devices is above +0.7 V; no oscillations were observed for negative bias. Oscillations were not observed for any bias in the symmetric devices. The zero-crossing voltages were independent of temperature and relative magnetization angle between the two ferromagnetic layers. A model using spin-split free electron energy bands in the ferromagnets and a trapezoidal tunnel barrier demonstrates qualitative agreement with the experimental data.

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Authors

  • Casey W. Miller

    Physics Dept., Univ. Calif. San Diego

  • Johan Akerman

    Dept. of Materials Physics, Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden

  • Zhi-Pan Li

    Physics Dept., Univ. Calif. San Diego

  • Ivan K. Schuller

    Physics Department, University of California-San Diego, 9500 Gilman Drive, La Jolla CA 92093-0319, USA, Physics Dept., Univ. Calif. San Diego, 9500 Gilman Dr., La Jolla CA 92093, Physics Department, UC San Diego, La Jolla, CA 92093, Physics department, University of California, San Diego, La Jolla, Department of Physics, University of California at San Diego, La Jolla CA 92093