Patent ID: 7601443

Claim:
A perpendicular magnetic recording medium comprising: a substrate; a perpendicular magnetic recording layer disposed on the substrate; and a soft magnetic underlayer (SUL) interposed between the substrate and the perpendicular magnetic recording layer, the soft magnetic underlayer comprising, a first magnetic layer and a second magnetic layer having unidirectional magnetic anisotropies in directions opposite to each other by an exchange bias; an antiferromagnetic layer interposed between the first magnetic layer and the second magnetic layer; a non-magnetic layer disposed at least on one of the first magnetic layer and the second magnetic layer; and a third magnetic layer disposed on the non-magnetic layer and antiferromagnetically bonded to the at least one of the first and second magnetic layers which has the non-magnetic layer disposed thereon, to have a uniaxial magnetic anisotropy, wherein the first magnetic layer is farther from the substrate than the second magnetic layer, and wherein the second magnetic layer has a saturation magnetization greater than a saturation magnetization of the first magnetic layer.