Patent ID: 7846563

Claim:
A perpendicular magnetic recording medium for the recording of data by the magnetization of regions of the medium by a magnetic write field from a magnetic write head, the 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; 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 less than the magnetic write field and less than 70 percent of the anisotropy field of the first ferromagnetic layer to enable non-coherent reversal of the magnetizations of the first and second ferromagnetic layers, whereby the magnetization of the second ferromagnetic layer reverses first in response to the magnetic write field and applies a torque to the first ferromagnetic layer to assist in reversal of the magnetization of the first ferromagnetic layer, the first ferromagnetic layer being located between the substrate and the second ferromagnetic layer; and a coupling layer (CL) between and in contact with the first ferromagnetic layer and the second ferromagnetic layer for reducing interlayer exchange coupling between the first and second ferromagnetic layers to enable said non-coherent reversal of the magnetizations of the first and second ferromagnetic layers; and a ferromagnetic oxide-free lateral coupling layer (LCL) between the substrate and the first ferromagnetic layer and in contact with the first ferromagnetic layer, the LCL comprising a granular material having intergranular exchange coupling greater than the intergranular exchange coupling of the first ferromagnetic layer with which it is in contact.