Spin Dynamics: Fast Switching of Macro-spins
Recent progress on the theoretical studies of fast magnetization reversal of Stoner particles is reviewed. The following results are discussed: (1) The Stoner–Wohlfarth (SW) limit becomes exact when the damping constant is infinitely large. Under the limit, magnetization moves along the steepest energy descent path. (2) For a given magnetic anisotropy, there is a critical damping constant, above which the minimal switching field is the same as that of the SW-limit. (3) The field of a ballistic magnetization reversal should be along a certain direction window in the presence of energy dissipation. (4) Since a time-dependent magnetic field can be an energy source, two new reversal strategies are possible. One is to use a field following magnetization motion, and the other is to use a circularly polarized microwave near the ferromagnetic resonance frequency. The critical switching fields of both strategies are substantially lower than that of precessional reversal for realistic materials. (5) The theoretical limits for both field-induced and current-induced magnetization reversal are presented for uniaxial Stoner particles.
KeywordsMagnetic Anisotropy Target State Magnetization Reversal Easy Axis Spin Current
This work is supported by UGC, Hong Kong, through RGC CERG grants #603007, 603106, 603508, and RPC07/08.SC03. We would also like to thank APS for granting us permission to use some materials in our early publications in APS journals.
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