Domain-wall dynamics in thick Permalloy films

Abstract

Micromagnetic numerical simulations are extended to study domain-wall structures and dynamics in micron-thick Permalloy films with an in-plane anisotropy easy axis. The equilibrium domain-wall structure is a flux-closure vortex elongated along the film thickness direction for films thicker than 2 μm. The dynamics of such a vortex wall under an easy-axis field is studied to yield velocity dependence and wall mass. The effect of eddy current damping is simplified by including a larger damping constant in addition to the intrinsic spin damping. With large damping, the steady-state wall structure is more stabilized under applied fields. Under a hard-axis field, wall structure transitions take place for small damping and low-frequency fields; for large damping and higher-frequency fields, these transformations are more suppressed, and the flux conduction is dominated by magnetization rotations instead of wall motions.