Spin transfer in bilayer magnetic nanopillars at high fields as a function of free-layer thickness

W. Chen, M. J. Rooks, N. Ruiz, J. Z. Sun, A. D. Kent

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    Abstract

    Spin transfer in asymmetric Co-Cu-Co bilayer magnetic nanopillars junctions has been studied at low temperature as a function of free-layer thickness. The phase diagram for current-induced magnetic excitations has been determined for magnetic fields up to 7.5 T applied perpendicular to the junction surface and free-layers thicknesses from 2 to 5 nm. The junction magnetoresistance is independent of thickness. The critical current for magnetic excitations decreases linearly with decreasing free-layer thickness, but extrapolates to a finite critical current in the limit of zero thickness. The limiting current is in quantitative agreement with that expected due to a spin-pumping contribution to the magnetization damping. It may also be indicative of a decrease in the spin-transfer torque efficiency in ultrathin magnetic layers.

    Original languageEnglish (US)
    Article number144408
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Volume74
    Issue number14
    DOIs
    StatePublished - Oct 13 2006

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    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics

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