Dual Segregant Perpendicular Recording Media With Graded Properties

We have introduced structural and magnetic gradations into the granular layer in capped media to promote incoherent switching and hence reduce the contribution of the cap layer to writeability improvement. X-ray photoelectron spectroscopy and transmission electron microscopy revealed that the granular layer was composed of two different microstructures: a well-isolated structure with Si-oxide and Cr-oxide at the bottom portion and a less isolated structure with Si-oxide at the top portion. We found that the graded media exhibit better adjacent track interference (ATI) performance than the conventional media in similar overwrite, magnetic core width, and bit error rate conditions. The graded media have shallower angular dependence of remanent coercivity while maintaining small magnetic cluster size, which is probably the main reason for the improved ATI performance.