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.

The domain configurations on the air-bearing surface (ABS) of inductive thin-film recording heads were studied. It was found that, instead of being a single domain structure, the ABS of a thin-film head usually has multidomains. The direction of the domain walls is neither parallel nor perpendicular to the gap plane. The magnetization was found to be in the plane of the ABS along the track width, with the magnetizations on the two sides of the domain walls either "head-to-head" or '"tail-to-tail." The domain walls are slanted in order to spread the magnetic charges along the wall over a larger region, thereby reducing magnetostatic energy in this configuration. The responses of the domain walls are not all in phase, and they are generally out of phase with the rotational process along the gap edge. The magnetization configuration on the ABS and in the throat and the sloped region were investigated in one. head and correlated with the domain walls on the ABS.