Correlation of microstructure, intrinsic magnetization switching properties, and recording performance in exchange-coupled composite media

Abstract

The analytical model for the intrinsic coercive squareness parameter, Sint* was applied to hard–soft stacked exchange-coupled composite media, and correlations with the microstructure and switching were studied. Thickening the hard magnetic layer in the composite stack led to a decrease in Sint*, as did thickening the NiW seed layers. However, this decrease was masked by thermal effects at the normal magnetometry time-scales of measurement. Upon thickening the soft layer in the composite stack, Sint* increased sharply at first and then only slightly. In contrast, the extent of incoherent switching, estimated from the peak value of the minor loop slope, increased slowly at first, and then sharply. The changes in Sint* and switching are correlated to the microstructure, particularly, grain size effects for the NiW series and growth effects for the hard–soft composite media series. Media signal-to-noise ratio at low recording frequencies, and adjacent track interference also show correlations with Sint*.