Control of magnetic anisotropy in Fe-Co-B soft magnetic underlayer for perpendicular magnetic recording media

摘要

Anisotropic residual stress induced in the Fe-Co-B/Ni-Fe layers causes high anisotropy field H_k in the films induced by magnetoelastic effect. The origin of residual stress in Fe-Co-B/Ni-Fe layers was investigated. The direction of magnetic anisotropy of Fe-Co-B/Ni-Fe layers was formed in the direction corresponding to the incident direction of sputtered particles reached substrate. The magnitude of the H_k depended strongly on the condition of argon gas pressure. An incident direction of sputtered particles, which has an important effect on the direction of H_k, seemed to be dispersed under high Ar gas pressure condition because of the increase of collision number between sputtered particles and Ar particles. However, a low gas pressure condition of 1 mTorr in which sputtered particles have a long mean free path led to restrain the dispersion of H_k direction. As a soft magnetic underlayer of high H_k, the noise level of the media with Fe-Co-B/Ni-Fe decreased about 4 dB compared to that with the layer of low H_k in low frequency.