Frequency dependence of overwrite saturation

Summary form only given. The frequency dependence of overwrite of a write head has been studied before both experimentally and theoretically. In those studies, the overwrite ratio was treated as a single parameter, presumably measured at some nominal writer operating current. However, the overwrite ratios are known to change with the write current, reaching a maximum value when the head fully saturates. In this work, we look at the entire overwrite vs. write current relationship and study the frequency dependence of this relationship. In order to accomplish this, the head saturation behavior is first calculated using the TOSCA software package, a finite element magnetostatic analysis tool from Vector Fields, Inc. This calculation yields sizes of the write field bubbles under different write currents. Next we develop an analytical overwrite model based on timing shifts due both to the hard transition shift and the shift from the old, low frequency transitions in the upstream direction. Then we use the write bubble sizes calculated from the TOSCA modeling in the hard transition shift analysis to arrive at the write current-overwrite relationships for different overwriting and overwritten frequencies.