Bloch line influence on wall motion response in thin-film heads

Abstract

We describe a new dynamic response behavior of domain walls in the permalloy of thin-film inductive heads. A laser magneto-optic microscope (LAMOM) which enhances the longitudinal Kerr effect, is used to image Bloch lines (BLs) within the 180°walls by aligning the optical plane of incidence perpendicular to these walls. BLs are visible due to the reversal in the Néel-type surface components of the wall magnetization at the BL position. Current pulses with fast transition times and ac currents within the frequency range of 1-10 MHz are applied to the integrated coil windings. Continuous excitation induces either a continuous flowing of the wall network or a temporary displacement. When individual pulses are applied, displacements of BLs are observed. Correlation of wall displacements with the BL displacements is demonstrated for some pulsed excitations.