Patent ID: 7147942

Claim:
A perpendicular magnetic recording medium comprising: a nonmagnetic substrate; and at least a seed layer, a nonmagnetic underlayer, a magnetic layer, and a protective film sequentially laminated on the substrate, wherein the seed layer is composed of a metal or alloy containing a face centered cubic (fcc) crystal structure selected from at least one element of Ni, Cu, Au, Pd, Pt, and Ir, wherein the nonmagnetic underlayer is composed of a metal or alloy having a hexagonal closest-packed (hcp) crystal structure, wherein the magnetic layer consists essentially of ferromagnetic crystal grains and a nonmagnetic grain boundary region, the nonmagnetic grain boundary region being composed of an oxide surrounding the ferromagnetic crystal grains, wherein the ferromagnetic crystal grains are composed of an alloy containing at least cobalt and platinum, and wherein a volume occupied by the grain boundary region falls within a range of 15% to 40% of a total volume of the magnetic layer, and a coercive force (Hc) thereof is greater than 3000 Oe and no higher than about 3700 Oe.