Dynamics of Spontaneous Magnetization Reversal in Exchange Biased Bilayers

ORAL

Abstract

We observe a temperature-driven magnetization reversal of a ferromagnet (FM= Ni, Co) magnetization under a constant magnetic field, when it is exchange biased by an antiferromagnet (AF=FeF$_{2})$. We attribute this phenomenon to the competition of the AF interfacial coupling and the FM Zeeman energy. This striking behavior allows us to investigate the AF dynamics through the FM reversal behavior. We found that the magnitude of FM reversal for a given cooling field strongly depends on the cooling speed, and the wait time around the N\'{e}el temperature. This shows the magnetic viscosity of the AF around its phase transition temperature. Moreover, by thermal cycling, the FM exhibits successive spontaneous reversal. This thermal training effect further points to high energy barriers resulting in slow dynamic processes of the system.

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Authors

  • Zhi-Pan Li

    Physics Dept., Univ. Calif. San Diego

  • Casey W. Miller

    Physics Dept., Univ. Calif. San Diego

  • Igov V. Roshchin

    Physics Department, UCSD, La Jolla, CA

  • 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