Electroless-deposited soft magnetic underlayer on silicon disk substrate for double-layered perpendicular magnetic recording media

A novel fabrication process of a soft magnetic underlayer (SUL) for a double-layered perpendicular magnetic recording medium was presented. The CoNiFeB SUL was deposited on a silicon disk substrate using an electroless deposition. The Ni seed layer for the electroless deposition was prepared by an electrochemical process. The surface of the deposited SUL was subjected to a chemical mechanical polishing to be flattened, and Ra value of the SUL was less than 0.4 nm. A magnetic domain structure greatly depended on the electroless deposition condition. Particularly, the control of an agitation speed during electroless deposition is much effective for the suppression of distinct domain walls appearing in CoNiFeB underlayers.