Domain structures and dynamics near the backgap closure of thin-film heads

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Abstract
Statically unstable spikelike reversed magnetic domains emanating from the backgap closure of thin‐film heads have been observed with high‐frequency (1–20 MHz) and high‐current amplitude (20–80 mA p‐p) drive fields by using a wide‐field magneto‐optic domain observation system with a 10‐nsec exposure time. The spikelike domains are repeatedly nucleated and annihilated within the drive cycle and do not remain after removal of the excitation. The formation of spikelike domains is due to the magnetization rotation back to the nearest easy directions after fanning out near the backgap closure to carry the spreading flux out of (or converging flux into) the backgap closure. The spikelike domains block the flux flow into and out of the backgap closure at excitation frequencies above 10 MHz due to the slow domain annihilation process. It is speculated that occasional failure of these spikelike domains to annihilate after a write pulse could lead to noise when they suddenly collapse during read out.