Patent ID: 8705208

Claim:
A perpendicular magnetic recording medium (PMRM), comprising: a substrate; a soft magnetic underlayer formed above the substrate; an underlayer formed above the soft magnetic underlayer; a magnetic layer formed above the underlayer, the magnetic layer comprising Co, Cr, Pt, and oxides thereof; a ferromagnetic metal layer formed above the magnetic layer, the ferromagnetic metal layer comprising Co, Cr, and Pt, wherein the ferromagnetic metal layer does not include oxides, wherein the underlayer controls orientation and segregation of the magnetic layer, wherein the magnetic layer having oxides comprises a first magnetic layer and a second magnetic layer nearer to the ferromagnetic metal layer than the first magnetic layer, wherein the first magnetic layer has a granular structure in which oxides surround ferromagnetic grains therein, wherein a Cr concentration of the second magnetic layer is between 26 at. % and about 32 at. %, wherein the Cr concentration of the second magnetic layer is greater than a Cr concentration of the first magnetic layer, wherein a difference between the Cr concentration of the first magnetic layer and a Cr concentration of the second magnetic layer is less than about 25 at. %, and wherein a nucleation field is larger than about 159.2 kA/m.