Patent ID: 7691500

Claim:
A perpendicular magnetic recording medium, wherein a perpendicular magnetic layer is formed by way of a soft-magnetic underlayer above a disk-shaped substrate having an opening at the center wherein the soft-magnetic underlayer comprises a first amorphous soft magnetic layer and a second amorphous soft magnetic layer separated from each other by a non-magnetic layer, the first soft magnetic layer and the second soft magnetic layer comprise a material having a negative magnetic strain constant and are antiferromagnetically exchange-coupled by way of the non-magnetic layer, and wherein an average value of an angle formed between the easy magnetization axis of the soft-magnetic underlayer and the radial direction of the substrate in the circumference at an identical radius is within 5 degrees; wherein the soft magnetic layer consists of FeCo at a combined 50 at % to 70 at % for the Fe and Co compositional ratio, and an additional amount of Ta and Zr; wherein Ta is X at % and the additional amount of Zr is Y at %, with X>10 and Y<X/2−1.