Patent ID: 8367230

Claim:
A perpendicular magnetic recording medium comprising: a nonmagnetic substrate; at least one soft magnetic layer formed on the nonmagnetic substrate; a first nonmagnetic underlayer formed on the soft magnetic layer, consisting of a fine crystal structure which is an aggregation of fine crystal grains of 1 to 3nm in diameter, and comprises a first Pd-Si layer formed on a side of the soft magnetic layer, and a second Pd-Si layer formed on the first Pd-Si layer and different in composition ratio from the first Pd-Si layer, and the Si content in the first Pd-Si layer is not less than 10 at%, and the Si content in the second Pd-Si layer is less than 10 at%; a second nonmagnetic underlayer formed on the first nonmagnetic underlayer, and made of one of ruthenium and a ruthenium alloy; and a perpendicular magnetic recording layer formed on the second nonmagnetic underlayer.