Switching dynamics in a thin film recording head

Abstract

The switching dynamics in a thin-film head for both the writing and reading modes are studied. To minimize magnetostatic energy, the film head is split up into multidomains subsequent to saturation writing in the hard (or track) direction. The domain structure is composed of elongated domains in the easy direction and closure domains at the edges. The results of our calculation show that domain wall motion contributes increasingly to the effective head permeability as the track width is decreased. In the readback process, it was found that the switching time for wall motion τ w (∼170 ns) in the edge domains is some two orders of magnitude larger that τ r for rotation (∼1 ns) in the main domains. Since these motions are coupled due to the requirement of continuity of the perpendicular component of \overrightarrow{M_{s}} at a 90° wall, the switching dynamics is dominated by wall motion. A finite distribution of wall motion threshold field H o can give rise to different time delays in the head response, leading to distortions in the readback signal, including the presence of wiggles at the trailing edge.