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Publication Citation: Phenomenological Theory of Current-Induced Magnetization Precession

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Author(s): Mark D. Stiles; J Xiao; A Zangwill;
Title: Phenomenological Theory of Current-Induced Magnetization Precession
Published: February 13, 2004
Abstract: We solve appropriate drift-diffusion and Landau-Lifshitz-Gilbert equations to demonstrate that unpolarized current flow from a non-magnet into a ferromagnet can produce a precession-type instability of the magnetization. The fundamental origin of the instability is the difference in conductivity between majority spins and minority spins in the ferromagnet. This leads to spin accumulation and spin currents that carry angular momentum across the interface. The component of this angular momentum perpendicular to the magnetization drives precessional motion that is opposed by Gilbert damping. Neglecting magnetic anisotropy and magnetostatics, our approximate analytic and exact numerical solutions using realistic values for the material parameters show (for both semi-infinite and thin film geometries) that a linear instability occurs when both the current density and the excitation wave vector parallel to the interface are neither too small nor too large. For many aspects of the problem, the variation of the magnetization in the direction of the current flows makes an important contribution.
Citation: Physical Review B (Condensed Matter and Materials Physics)
Volume: 69
Issue: 5
Keywords: current-induced torque;magnetic instability;magnetic multilayers;precession;spin current;spin current;spin waves;spin-transfer torque
Research Areas: Nanomagnetics
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