Film-head pulse distortion due to microvariation of domain wall energy

Experiments show that the location of spurious peaks on the trailing edges of data pulses is strongly influenced by the application of small DC bias currents to the head coil during readback. A simple model of the head response which includes both magnetization rotation and domain wall motion for the case where domain wall coercivity is comparable to signal fields in the head reproduces many of the features of the observations. Calculations show that fields in pole tips during reading can exceed the wall-motion coercive force of permalloy. It is demonstrated that the resulting domain wall motion could give rise to the spurious signals sometimes seen in thin-film heads. It is proposed that such heads contain domain walls parallel to the signal flux path. The observed oscillations in the spurious response are primarily caused by filter dynamics, not domain wall dynamics.<
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