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.

• Received 15 April 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.3653