Patent ID: 9240204
Filing Date: 2016-01-19
CPC Classification: C23C,G11B

Claim Text:
1. A perpendicular magnetic disk comprising: on a base and in the order from bottom, a first granular magnetic layer group consisting of a plurality of magnetic layers each having a granular structure; a non-magnetic layer having Ru or a Ru alloy as a main component; a second granular magnetic layer group consisting of a plurality of magnetic layers each having the granular structure; and an auxiliary recording layer having a CoCrPtRu alloy as a main component, wherein the magnetic layers of the first granular magnetic layer group that are closer to a top surface of an uppermost layer of the first granular magnetic layer group have an equal or smaller content of Pt than the magnetic layers of the first granular magnetic layer group that are closer to a bottom surface of a lowermost layer of the first granular magnetic layer group, wherein the magnetic layers of the second granular magnetic layer group that are closer to a top surface of an uppermost layer of the second granular magnetic layer group have an equal or smaller content of Pt and have a larger content of an oxide than the magnetic layers of the second granular magnetic layer group that are closer to a bottom surface of a lowermost layer of the second granular magnetic layer group, wherein the lowermost layer of each of the first granular magnetic layer group and the second granular magnetic layer group contains Cr wherein a second lowermost layer of each of the first granular magnetic layer group and the second granular magnetic layer group contain SiO wherein the first granular magnetic layer group, the second granular magnetic layer group and the auxiliary recording layer satisfy the following requirement: wherein T