Grooved soft-underlayer for double-layered medium

In order to realize high track density, a soft-underlayer (SUL) with land-and -groove shape for double-layered medium has been investigated. Both the spread and the path of magnetic flux from the head can be constrained by the land of the SUL, hence the grooved SUL seems advantageous for high track density recording showing robustness against a track misregistration. Furthermore, the recording field distribution in track width direction can be straightforward so as to limit the curvature of the recorded bit line.