Perpendicular magnetic recording medium with an exchange-spring recording structure and a lateral coupling layer for increasing intergranular exchange coupling

A perpendicular magnetic recording medium for use in a magnetic recording system having a write head that generates a magnetic write field to magnetize regions of the medium, 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;
• and
• 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;
• a coupling layer (CL) between the first ferromagnetic layer and the second ferromagnetic layer and permitting ferromagnetic exchange coupling of the first ferromagnetic layer with the second ferromagnetic layer, whereby in the presence of a magnetic write field the magnetization in a region of the second ferromagnetic layer reverses first and assists in the magnetization reversal in a region of the first ferromagnetic layer;
• and
• a ferromagnetic lateral coupling layer (LCL) between the CL and the second ferromagnetic layer and in contact with the CL and the second ferromagnetic layer, the LCL comprising a granular material having intergranular exchange coupling greater than the intergranular exchange coupling of the second ferromagnetic layer with which it is in contact.