Eddy current plus spin-dynamical limitations to switching speed in thin-film heads

The author considers the combined influence of eddy currents plus spin dynamics on limiting the quasi-coherent rotational switching speed of thin-film heads. The results represent lower physical limits, and exclude potentially slower and more complex incoherent reversal mechanisms. A simplified head model employs the 1-D eddy current diffusion equation coupled to the planar form of Gilbert´s equations for spin dynamics. Effects of head saturation and internal demagnetization fields are included. When Γ≠t_e ω_r=(eddy current diffusion time)×(spin resonance frequency) is of the order 100, numerically integrated results for the time-dependent, volume-averaged magnetization <M(t)> can be described by two simple analytical models applicable to cases where the applied reversing field H _a⩽H_sat, or H_a≫ H_sat, where H_sat is that field required to saturate the yoke. For Γ⩽10, the eddy current models progressively fail due to the influence of spin-inertia