Cap-Induced Magnetic Anisotropy in Ultra-thin Fe/MgO(001) Films

ORAL

Abstract

Magnetic anisotropy plays an important role in the design of spintronic devices. Perpendicular magnetic anisotropy (PMA) is preferred for magnetic tunnel junctions because the resulting energy barrier between magnetization states can be very high and this allows enhanced device scalability suitable for magnetic random access memory applications. Interface induced anisotropy is often used to control magnetic easy axes. For example, the Fe/MgO(001) system has been predicted to exhibit PMA in the ultrathin Fe limit. We have used \textit{in-situ} magneto optic Kerr effect and \textit{ex-situ} SQUID to study the changes in anisotropy constants between bare Fe/MgO(001) films and those capped with MgO, Pt, and Ta. In some cases in-plane anisotropy terms reverse sign after capping. We also observe transitions from superparamagnetic to ferromagnetic behavior induced by capping layers. Perpendicular anisotropy is observed for Pt/Fe/MgO(001) films after annealing to 300\textdegree C. These effects are characterized and incorporated into a magnetic simulation that accurately reproduces the behavior of the films.

*This work was supported in part by the Semiconductor Research Corporation programs (1) MSR-Intel, and (2) C-SPIN.

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Authors

  • Tobias Brown-Heft

    • Materials Department, University of California Santa Barbara

  • Mihir Pendharkar

    • Electrical and Computer Engineering Department, University of California Santa Barbara

  • Elizabeth Lee

    • Engineering Department, Harvey Mudd College, Claremont, CA

  • Chris Palmstrom

    • California NanoSystems Institute, University of California Santa Barbara
    • Materials Department, Department of Electrical and Computer Engineering, University of California at Santa Barbara
    • Materials Department, University of California-Santa Barbara, Santa Barbara, California 93106, USA
    • Electrical and Computer Engineering Department & Materials Department, University of California Santa Barbara
    • Materials Department and Department of Electrical and Computer Engineering, Univ of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara