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.

*Supported by US Department of Energy. In collaboration with Freescale Semiconductor.

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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