Switching volume change and recording performance correlation for weakly coupled exchange spring media

We employed a new field sweep ratio dependence analysis method on the polar Kerr loop of exchange spring media to estimate the short time switching field, H0, and thermal stability factor, KUV/kBT, at various normalized Kerr signal levels, M, using modified Sharrock’s equation. For weakly coupled media, we observed that large switching volume changes around a “kink” in the Kerr loops. We observed a rapid increase in the KUV/kBT values before the kink, which suggests rapid switching of large areas of the soft layer via domain wall propagation. Small interfacial decoupling in exchange spring media between the soft and hard layers showed large degradation in media writability.