Magnetization Reversal in Ultrathin Films with Monolayer-Scale Surface Roughness.

The intrinsic anisotropy of nominally flat, ultrathin ferromagnetic films typically is augmented by a uniaxial anisotropy at step edges. We report model calculations of hysteresis for such systems with in-plane magnetization and monolayer scale roughness. The reversal process is a combination of domain nucleation at step edges, expansion of these domains through morphological constrictions, and coherent rotation within domains. The initiation of reversal at well-separated step edges can explain the very small coercive fields measured for real ultrathin magnetic films. 75.70.-i,75.60.-d Typeset using REVTEX