Stray field sensitivity of perpendicular recording heads

Abstract

An effect of stray field on perpendicular head performance was studied by three-dimensional finite-element method modeling. Perpendicular writers in a drive are exposed to the stray field up to 20 Oe, which generates an erase field in double layer media. The coefficient of a stray field magnification by writer can be of several dozens. Main and return poles of the writer generate the same polarity erase field in the media but the field is stronger under the main pole due to considerably smaller pole size at an air-bearing surface (ABS). The erase field depends on parameters of the media such as keeper permeability μK and head-keeper spacing (HKS) but is not sensitive to keeper thickness. The erase field exhibits a maximum at μK≈20 and decreases with μK or HKS increase. An incident angle of the stray field relatively to a medium plane substantially affects the field strength exhibiting a maximum at about 30° from normal for conventional single pole writer. The recess of the return pole from the ABS causes a strong increase of the erase field at the main pole. The field more than doubles when the return pole has 0.5 μm recess. The erase field can be controlled by writer design optimization. Simulation of stray field sensitivity and efficiency for a conventional single pole and cusp-field writers and their modifications has shown that the cusp-field writer has the lowest sensitivity to the stray field but slightly lower efficiency than conventional writer.