Patent ID: 8802247

Claim:
A perpendicular magnetic recording medium comprising: a soft magnetic underlayer, an intermediate layer, a magnetic recording layer, and a protective layer which are laminated, in order, on a substrate, wherein said soft magnetic underlayer has an upper soft magnetic layer having a first soft magnetic layer, and a second soft magnetic layer below and in direct contact with the first soft magnetic layer, wherein said soft magnetic underlayer has a lower soft magnetic layer having a third soft magnetic layer, and a fourth soft magnetic layer disposed below and directly adjacent said third magnetic layer, wherein said soft magnetic underlayer has a non-magnetic layer formed between said upper soft magnetic layer and said lower soft magnetic layer, wherein said second soft magnetic layer and said third soft magnetic layer are antiferromagnetically coupled to each other, said first soft magnetic layer being composed of an amorphous alloy containing 85 at. % or less of Co and 15 at. % or more of a non-magnetic material; and said second and third soft magnetic layers being composed of an alloy containing more than 85 at. % of Co and 15 at.% or less of a non-magnetic material, wherein said first and fourth soft magnetic layers are each Co—Ta—Zr—Cr, wherein said second and third soft magnetic layers are Co—Ta—Zr, wherein a ratio of magnetic moments of the upper and lower soft magnetic layers are about equal wherein the thickness of said first soft magnetic layer is 15 nm or more, wherein the thickness of said second soft magnetic layer is 5 nm or more.