Patent ID: 7875373

Claim:
A perpendicular magnetic recording medium comprising: an underlayer, an intermediate layer, a recording layer, and a protective layer, deposited, in order over a substrate, wherein the recording layer includes a layer which consists of crystal grains mainly composed of cobalt and crystal grain boundaries mainly composed of an oxide, wherein an oxygen content of the recording layer changes along the film thickness direction, the oxygen content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is lower than the oxygen content of an area of about 4 nm in the vicinity of the center of the recording layer, and the oxygen content in an area of 4 nm from the interface between the recording layer and the protective layer is lower than 5 at % and lower than the oxygen content in the area of about 4 nm in the vicinity of the center of the recording layer, and wherein the recording layer contains chromium, a mean chromium content in the recording layer changes along the film thickness direction, and the mean chromium content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is higher than the mean chromium content in an area of about 4 nm in the vicinity of the center of the recording layer.