Magnetic recording medium and magnetic storage device

A magnetic recording medium comprising:

• a non-magnetic substrate;
• a first underlayer having an amorphous or microcrystal structure disposed on the non-magnetic substrate;
• a second underlayer disposed on the first underlayer, the second underlayer comprising a Cr—Ti—B alloy containing Cr as a main component, and from 2% to 12% by atomic weight B,
• a lower magnetic layer disposed on the second underlayer, the lower magnetic layer containing Co as a main component and from 10% to 16% by atomic weight Cr, and having a film thickness of from 1.5 nm to 4.5 nm;
• a non-magnetic intermediate layer disposed on the lower magnetic layer;
• and
• an upper magnetic layer disposed on the non-magnetic intermediate layer, the upper magnetic layer containing Co as a main component, and being and antiferromagnetically coupled with the lower magnetic layer.

A magnetic recording medium comprising:

• a non-magnetic substrate;
• a first underlayer having a B2 structure disposed on the non-magnetic substrate;
• a second underlayer comprising a Cr—Ti—B alloy containing Cr as a main component and from 2% to 12% by atomic weight of B, the second underlayer being disposed on the first underlayer;
• a lower magnetic layer disposed on the second underlayer, the lower magnetic layer containing Co as a main component and from 10% to 16% by atomic weight Cr, and having a film thickness of from 1.5 nm to 4.5 nm;
• a non-magnetic intermediate layer disposed on the lower magnetic layer;
• and
• an upper magnetic layer disposed on the non-magnetic intermediate layer, the upper magnetic layer containing Co as a main component and being antiferromagnetically coupled with the lower magnetic layer.

A magnetic recording medium comprising:

• a non-magnetic substrate;
• a first underlayer having an amorphous or B2 structure disposed on the non-magnetic substrate;
• a second underlayer disposed on the first underlayer, the second underlayer containing Cr as a main component and from 2% to 12% by atomic weight B;
• a non-magnetic third underlayer disposed on the second underlayer, the third underlayer having a hexagonal close-packed structure and containing Co as a main component;
• a lower magnetic layer disposed on the third underlayer, the lower magnetic layer containing Co as a main component and from 10% to 16% by atomic weight Cr and having a film thickness from 1.5 nm to 4.5 nm;
• a non-magnetic intermediate layer disposed on the lower magnetic layer;
• and
• an upper magnetic layer disposed on the non-magnetic intermediate layer, the upper magnetic layer containing Co as a main component and being antiferromagnetically coupled with the lower magnetic layer.