Computer simulation of domain wall motion in a magnetic strip line with submicron width

Abstract

The dynamics of magnetization reversal in a very narrow ferromagnetic wire was investigated by micromagnetic computer simulation. The calculation was performed both for an isolated finite-length wire and for an infinitely long wire which contained a domain wall in a portion. In the former calculation, a remanent equilibrium domain configuration was, at first, derived from a uniformly magnetized configuration. Then a reversal field was applied along the wire so as to nucleate and move the domain walls. A reversal field of a hundred and several tens Oe was necessary to nucleate a moving wall. It was found that the head of the moving wall had the shape of a wedge and that the wall dynamically changed its structure while moving. In the latter calculation, the mechanism of wall motion and the wall velocity at lower driving fields were evaluated. When the driving field was small enough, the wall moved with keeping its magnetic structure. The wall velocity became higher with increasing the width or decreasing the thickness of the wire. In the application of higher fields, however the wall structure changed dynamically, and the wall velocity was almost twice as large as that in the steady-state motion.