Overwrite in thin film disk recording systems

Abstract

Overwrite in thin film rigid disk recording has been studied experimentally using disks with a wide range of magnetic moment and coercivity. Standardh/J overwrite was investigated in detail at various recording currents and different flying heights. A theoretical model was developed using simple analytical approximations that relate demagnetization-field-induced position shift (hard transition shift) to the measured overwrite. The demagnetization fields due to the leading edge transitions were calculated analytically including a good approximation to the gapped head image. The results compare well with experimental measurements. A new overwrite measurement technique using the second harmonic component of a 0.5J signal is also described in this work.

The study of noise characteristics and overwrite on oriented and isotropic media

“…In spite of the thicker magnetic layer and wider PW,,, all the unoriented disks exhibit better OW than type A. This result is not consistent with the existing overwrite theory that OW is proportional to the "hard" transition shift [5]. According to the existing theory, at the same M,t and H,, the isotropic media should show degraded OW because of the thicker magnetic film compared with type A disks.…”

The recording characteristics of particulate double layers with hard-magnetic and soft-magnetic underlayers

“…It seems to have been reduced by the underlayer bringing about a magnetostatic interaction with the upper layer. In recent doublelayer studies [9,10], in which an ME underlayer is used with an MP upper layer, this also has been observed.…”

Analysis of side writing asymmetry

“…In the ME-1 sample, the on-track residue looks unchanged. In this sample, the on-track overwrite process is probably dominated by modulation, which is typical in thin media [7]. The embedded track is more difficult to erase in the MP samples, due to the thick magnetic layers.…”