Patent ID: 7601445

Claim:
A perpendicular magnetic recording medium comprising at least a nonmagnetic under layer, a magnetic layer, and a protective layer stacked on a nonmagnetic substrate, wherein said magnetic layer includes a ferromagnetic crystal grain and a nonmagnetic grain boundary region; said magnetic layer comprises a total of 0.1 to 30 mol % of oxides which form said crystal grain boundary region; said oxides which form said crystal grain boundary region comprises: at least one oxide selected from group A of Y oxides, W oxides, Mg oxides, Al oxides, Zr oxides, and Hf oxides; and at least one oxide selected from group B of Ti oxides, Ce oxides, Si oxides, Cr oxides, Ni oxides, and Ta oxides; and the content of the oxide selected from the group A in mole percentage is smaller than the content of the oxide selected from the group B in mole percentage in the oxides which form said crystal grain boundary region.