GRAIN INFLUENCES ON DOMAINS AND READ-BACK PULSE DISTORTIONS OF FERRITE MIG HEADS

Direct observations using micro-ellipsometry, Kerr microscopy, and ele ctron back-scatter diffraction are made for the first time on individu al grains in the leading pole-tip region of polycrystalline ferrite MI G heads intended for narrow track (less than or similar to 10 mu m) da ta recording. These observations, compared with readback-after-write w aveforms, indicate that waveform instabilities and asymmetry which can cause high error rate would be diminished by controlling grain size a nd orientation in this critical pole-tip region. When large grains (ne ar the gap) exceed the single domain size (similar or equal to 5 mu m) but are oriented so their media-facing surface contains an easy-axis of magnetization, the head produces smaller asymmetry and instability than when missoriented (large) gap grains or multiple single-domain si ze grains are present. This indication from a limited sampling of MIG heads appears consistent with polarized neutron and permeability measu rements on bulk polycrystalline ferrite and an understanding of surfac e domain behavior in single crystal ferrite MIG heads.