Magnetic reversal on vicinal surfaces

We present a theoretical study of in-plane magnetization reversal for vicinal ultrathin films using a one-dimensional micromagnetic model with nearest-neighbor exchange, fourfold anisotropy at all sites, and twofold anisotropy at step edges. A detailed ``phase diagram'' is presented that catalogs the possible shapes of hysteresis loops and reversal mechanisms as a function of step anisotropy strength and vicinal terrace length. The steps generically nucleate magnetization reversal and pin the motion of domain walls. No sharp transition separates the cases of reversal by coherent rotation and reversal by depinning of a $90\ifmmode^\circ\else\textdegree\fi{}$ domain wall from the steps. Comparison to experiment is made when appropriate.