An Influence of Head Field on the Transition Noise of Thin Film Disk

Abstract

The dependence of a field gradient on media noise was demonstrated. Medium noise was degraded under the influence of a secondary field with low field gradient. This influence was confirmed by the investigation of changes in media noise, which are based on the intrinsic micromagnetic media properties, for different field gradients. Reverse dc modulation noise and transition noise of low-H c and high-H c disks were evaluated using a single-sided MIG and a ferrite mini-monolithic head. Reverse dc modulation noise showed different values for the two heads, despite the fact that the medium was the same. The ratio of increase of reverse dc demagnetization noise to dc saturation noise, i.e. the reverse dc modulation ratio, was higher when the medium was evaluated using the MIG head, which can generate sharper field gradients in each medium. However, transition noise was lower when using the MIG head than when using the ferrite head. As a result, both the reverse dc modulation increase ratio and the transition noise level, which has been regarded as an intrinsic property of the medium, were strongly correlated to the field gradient.