Thermal reversal of exchange spring composite media in magnetic fields

For exchange coupled composite particles composed of a soft and a hard magnetic layer, the minimum energy paths between equilibrium states of the hysteresis loops are calculated using a path approach based on the nudged elastic band method. From the minimum energy paths the energy barriers for thermal reversal are determined as a function of the applied magnetic field. The field dependence of the energy barrier can be described approximately by power laws. Until reaching the saddle point for thermal reversal a domain wall is nucleated and compressed to the width of a wall propagating through a hard magnetic reference particle. (c) 2007 American Institute of Physics.