EDDY-CURRENT PLUS SPIN DYNAMIC LIMITATIONS TO SWITCHING SPEED IN THIN-FILM HEADS

This work 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 GAMMA = t(c)w(r) = (eddy current diffusion time) x (spin resonance frequency) is of order 100, numerically integrated results for the time-dependent, volume-averaged maguetization (M(t)) can be described by two simple analytical models applicable to cases where the applied reversing field H(a) less-than-or-equal-to H(sat), or H(a) >> H(sat), where H(sat) is that field required to saturate the yoke. For GAMMA less-than-or-equal-to the eddy current models progressively fail due to the influence of spin-inertia.