Patent ID: 7588841

Claim:
A perpendicular magnetic recording medium comprising: a substrate; an exchange-spring structure on the substrate and comprising: a first ferromagnetic layer comprising a granular polycrystalline cobalt alloy and an oxide of one or more of Si, Ta, Ti, Nb, Cr, V and B and having an out-of-plane easy axis of magnetization, the first ferromagnetic layer having regions capable of being magnetized perpendicular to the plane of the layer; a second ferromagnetic layer comprising a granular polycrystalline cobalt alloy and an oxide of one or more of Si, Ta, Ti, Nb, Cr, V and B and having an out-of-plane easy axis of magnetization and an anisotropy field equal to or greater than 70 percent and less than or equal to 90 percent of the anisotropy field of the first ferromagnetic layer, the first ferromagnetic layer being located between the substrate and the second ferromagnetic layer, the second ferromagnetic layer having regions capable of being magnetized perpendicular to the plane of the layer; a ferromagnetic lateral coupling layer (LCL) between the first ferromagnetic layer and the second ferromagnetic layer and in contact with the first ferromagnetic layer, the LCL comprising an oxide-free granular material having intergranular exchange coupling greater than the intergranular exchange coupling of the first ferromagnetic layer with which it is in contact; and an exchange-spring coupling layer (CL) between the LCL and the second ferromagnetic layer for facilitating the assistance of the magnetization reversal of regions of the first ferromagnetic layer by the magnetization reversal of regions of the second ferromagnetic layer.