Patent ID: 8329321

Claim:
A perpendicular magnetic recording medium comprising a nonmagnetic substrate, a first magnetic recording layer, a coupling layer disposed directly on the first magnetic recording layer, and a second magnetic recording layer disposed directly on the coupling layer, the first magnetic recording layer and the second magnetic recording layer being ferromagnetically coupled with a coupling energy controlled by the coupling layer to reverse individually magnetizations, and an axis of easy magnetization of the first magnetic recording layer and an axis of easy magnetization of the second magnetic recording layer being approximately perpendicular to a plane of the nonmagnetic substrate, wherein Ku 1 T 1 >Ku 2 T 2 when Hk 1 >Hk 2 , and Ku 1 T 1 <Ku 2 T 2 when Hk 1 <Hk 2 , where Hk 1 , Ku l , and T 1 are an anisotropy magnetic field, a uniaxial anisotropy constant, and a thickness of the first magnetic recording layer, respectively, and Hk 2 , Ku 2 , and T 2 are an anisotropy magnetic field, a uniaxial anisotropy constant, and a thickness of the second magnetic recording layer, respectively.