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

Abstract

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.

Ultrafast laser diagnostics and modeling for high-speed recording heads

“…A recently developed dynamic micromagnetic model by Sandler and Bertram [2] combines gyromagnetic effects and eddy currents, and is applied to the rise time problem in thin film write heads. Here we employ their approach to calculate the flux rise time as a function of yoke length.…”

“…The simulated head consists of tip, neck, and yoke regions as described in [2]. The yoke is modeled micro-magnetically, but the neck and tip regions are modeled with an equivalent 2 d, =(2n-1) i + j i w 6 (2) where pcL, is the intrinsic peameability, w and t stand for the cross section of a slab, 6 is the skin depth.…”

“…The yoke is modeled micro-magnetically, but the neck and tip regions are modeled with an equivalent 2 d, =(2n-1) i + j i w 6 (2) where pcL, is the intrinsic peameability, w and t stand for the cross section of a slab, 6 is the skin depth. pcL, is attributed to the magnetization damping and given by (3) where U ) is angular velocity, and 7 is a domain wall motion constant.…”

“…Ultrafast laser-based time-resolved scanning Kerr effect microscopy [ 11 gives current and "spoton-pole-tip'' magnetization profiles in the time-domain. A dynamic micromagnetic model [2], including gyromagnetic effects and eddy currents, yields rise times as a function of yoke length.…”

Lumped-element RC model for high-data-rate thin-film heads

“…Several studies on possible limitations on the data rate have been performed in the past years. They include works on the switching speed of the media [4], [5], fast writers [6], [7], as well as on the gyromagnetic effects and how they affect the speed at which the data can be retrieved [8]. Little attention has been paid to the effects of parasitic capacitance coupling through various head components.…”