Dynamic generalization of Stoner-Wohlfarth model

A dynamic generalization of the Stoner-Wohlfarth (SW) model is presented, i n which the applied field component h(az) parallel to the particle anisotro py axis is slowly varied, whereas the one in the perpendicular plane, h(a p erpendicular to), is rotated at the angular frequency omega. The Landau-Lif shitz-Gilbert equation is solved to calculate the system response under the constraint of spatially uniform magnetization at all times. Switching unde r slowly varying h(az) is discussed. Various switching modes can occur in c orrespondence of different types of bifurcation present in the dynamics. In addition, it is shown that the system response can become quasiperiodic, w ith spontaneous magnetization oscillations at a frequency definitely lower than omega. (C) 2001 American Institute of Physics.