Perpendicular magnetic recording media with magnetic anisotropy gradient and local exchange coupling

A stack, comprising:

• a substrate having at least one surface;
• and
• a layer stack on the surface of said substrate, the layer stack including a perpendicular recording layer comprising a plurality of columnar-shaped magnetic grains extending perpendicularly between opposing surfaces of the recording layer, each columnar-shaped magnetic grain comprising a plurality of sub-layers including:
• a first sub-layer comprising a first magnetic material and having a first magnetic anisotropy field Hk1;
• and
• a second sub-layer disposed on the first sub-layer, the second sub-layer comprising a second magnetic material and having a second magnetic anisotropy field Hk2, wherein Hk1>Hk2 and wherein at least one of the first and second materials comprises Fe.

An apparatus, comprising:

• a columnar-shaped magnetic grain comprising:
• a first magnetic layer comprising a first magnetic material and having a first magnetic anisotropy field, Hk1;
• a first spacer layer adjacent to the first magnetic layer;
• a second magnetic layer adjacent to the first spacer layer, the second magnetic layer comprising a second magnetic material and having a second magnetic anisotropy field, Hk2;
• a second spacer layer adjacent to the second magnetic layer;
• and
• a third magnetic layer adjacent to the second spacer layer, the third magnetic layer comprising a third magnetic material and having a third magnetic anisotropy field Hk3, wherein each of the first, second, and third magnetic materials differs from the other magnetic materials in one or both of composition and dopant concentration, and Hk1>Hk2 >Hk3, wherein each of the magnetic lavers has a perpendicular magnetic anisotropy field that is greater than at least about 1000 Oe.