Time-dependence effect in alumite recording media with perpendicular anisotropy

In this paper, we will present a study of the time-dependence effect in alumite perpendicular media at different; thicknesses. Important parameters of the time-dependence effect such as magnetic viscosity and activation volume are investigated. Viscosity as a function of applied field (viscosity curve) exhibits a short plateau at a low field and then decreases monotonously with increasing field. After correcting for the demagnetizing field, the shape of the intrinsic viscosity curves changes to the well-known shape of the viscosity curve of in-piano media, i.e., they have a peak near H-c. The intrinsic viscosity curves obtained from the experiments were fitted to an analytical model by Chantrell et al. [1], from which, we found that the effective switching volumes obtained by fitting are much smaller than the column volumes, indicating that the reversal mechanism is incoherent.