Switching volumes in high-density recording materials with different magnetization reversal modes

The switching volume of materials for recording media is obtained from meas urements of the time dependence of the magnetization, and related to the ma gnetization reversal mode. The switching, or activation, volume is large an d close to the physical size in particles with reversal similar to coherent rotation, and it decreases when the reversal is incoherent or heterogeneou s, or, with larger extent, in materials switching the magnetization by nucl eation. (C) 1999 Elsevier Science B.V. All rights reserved.