Effect of Domain Structure of Main Pole Film on Reproducing Sensitivity of SPT Head

The domain structures of narrow-track single-pole heads for perpendicular magnetic recording have been observed, and their effects on the reproducing sensitivities were investigated. The ratio of the double height 2h of the closure domain to the track width W increases when the track width and the anisotropy field Hk of a Co-Zr-Nb amorphous main pole film decrease. The maximum reproducing sensitivity for each narrow-track head is obtained for the optimum value of Hk, when the ratio of 2h to W is about 30 percent. When the Hk is smaller than the optimum value giving the maximum sensitivity, the reproduced voltage not only decreases but is also unstable, changing with every cycle of recording. On the other hand, the reproduced voltage is stable, and becomes smaller for larger values of Hk, because the permeability of the film decreases. The reproducing sensitivity of the narrow track single pole head, formed from film having the optimum Hk value, does not decrease even for heads with tracks 10 micron wide.