Effect of Exchange-Coupling on Switching Fields in Magnetic Recording

Increased levels of exchange in a thin-film granular perpendicular recording media generally lead to reduced coercivity. However, this behavior cannot be deduced simply from the mean-field theory. To gain some insights into this behavior, a simple 2-D chain-of-grains model is employed. It can be recognized that the reduction in coercivity is due to the presence of in-plane magnetization and the corresponding in-plane fields that arise at the transitions between magnetized regions. In addition, a comparison is made between the two classical forms for exchange energy, 1-cosθ and 1/2θ², that link adjacent grains. The latter form is found to have a much larger impact on coercivity and results in a more Kondorsky-like angular dependence.