High temperature annealing induced superparamagnetism in CoFeB/MgO/CoFeB tunneling junctions

ORAL

Abstract

We have investigated the evolution of the magnetic transport properties as a function of short annealing time in CoFeB/MgO/CoFeB based MTJ junctions with a free layer of 2 nm. It is found that the hysteresis behaviors in MR loops disappear in samples annealed for 17 minutes. The linear region between MR and the applied field gradually increases. The MR loops without hysteresis can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

*This work was supported by DOE DE-FG02-07ER46374 and NSF Grant No. DMR0827249.

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Authors

  • Xiaoming Kou

    • University of Delaware
    • Department of Physics and Astronomy, University of Delaware

  • Weigang Wang

    • Department of Physics and Astronomy, Johns Hopkins University

  • Xin Fan

    • University of Delaware
    • Department of Physics and Astronomy, University of Delaware

  • L.R. Shah

    • University of Delaware
    • Department of Physics and Astronomy, University of Delaware
    • Physics and Astronomy, University of Delaware, Newark DE, 19716

  • Rae Tao

    • Department of Physics and Astronomy, University of Delaware

  • John Xiao

    • University of Delaware
    • Department of Physics and Astronomy, University of Delaware