Micromagnetic simulations with eddy currents of rise time in thin film write heads

A dynamic micromagnetic model which includes gyromagnetic effects (via the Landau-Lifshitz equation) and eddy currents has been developed and applied to the rise time problem in thin film write heads. A cross-section of the part of the head covering the coils is simulated with this model, while the rest of the head is modeled as saturable reluctances. The reluctances do not include eddy currents, but they do include leakage, fringing and saturation, and allow for computation of the deep gap field. This model is used to study the details of the dynamics of the magnetization in the yoke as well as the dependence of rise time on geometric and material parameters. It is found that switching starts at the surfaces of the pole and moves inward in ''transition zones.'' Also, if rise time is defined as the time it takes the deep gap field to reach 7 kOe, the rise time increases with pole thickness but decreases with saturation magnetization and driving current. (C) 1997 American Institute of Physics.