Current-induced magnetization switching in small domains of different anisotropies

Several recent experimental studies have confirmed the possibility of switching the magnetization direction in small magnetic domains by pumping large spin-polarized currents through them. On the basis of equations proposed by Slonczewski for domains with uniform magnetization, we analyze the stability and switching in two cases which differ by the anisotropy type. One of anisotropy types corresponds to that of the existing experimental device. Qualitatively different behavior is found in shapes of bistable regions and regions with stable precession. Stabilization of unusual ``canted'' equilibria is found in one of the cases. The sensitivity of the switching pattern to a change in anisotropy pattern underscores the necessity of theoretical guidance for the interpretation of experimental results. We propose experiments to search for stabilized canted equilibria and precession cycles. Our study is analytic as opposed to recent numeric work and the method can be applied to other anisotropy patterns as the experimental interest develops.