Side writing phenomena in narrow track recording

Abstract

Understanding of side writing phenomena is of critical importance for narrow track recording. For typical planar isotropic films, it has been found that significant noise arises from track edges. Electron microscopy studies have shown that track edge patterns in planar isotropic films are significantly different from that in oriented film media. However, effects in the read back voltage and impacts on different detection mechanisms remain unclear. In this paper, computer simulation study of recording properties and noise behavior due to side writing for recoding media with various orientation ratio along the recoding track are presented. The recording media are chosen to be longitudinal thin films and an earlier developed micromagnetic model is utilized in the study. The film is represented by an array which contains 128x128 grains, corresponding to approximately 4μm x 3.6 μm with grain diameter D = 30nm. To resemble oriented film media, a Gaussian distribution of the angles between grain crystalline easy axes and the recording track direction is assumed with an angular dispersion Δ θ (standard deviation). In addition, the easy axes are constrained in the film plane. Films with Δ θ varied from 10° to 90° and with the easy axes randomly oriented in the film plane studied. Recording processes of di-bit transition pairs arc simulated using the Lindhom formula for a finite width ring head of 1.5μ wide. Reproduce voltage pulses are calculated using reciprocity theorem. The initial magnetization state before recording is a previously saturated state. The maximum head field inside the medium is approximately 3.5 times of the medium coercivity in a recording simulation.