Patent ID: 7482071

Claim:
A perpendicular magnetic recording disk comprising: a substrate; a layer of magnetically permeable material on the substrate; a nonmagnetic underlayer on the layer of magnetically permeable material and having a hexagonal-close-packed (hcp) crystalline structure; and a granular magnetic recording layer on the underlayer and having a hcp crystalline structure with the c-axis oriented substantially perpendicular to the recording layer, the recording layer comprising Co, Pt, Cr, and oxides consisting of oxides of Cr and Ta, said Cr oxides and Ta oxides being present primarily between the grains of the granular magnetic recording layer, wherein the amount of oxygen present in the recording layer is greater than about 22 atomic percent and less than about 35 atomic percent and the amount of Ta present in the recording layer is greater than about 2 atomic percent and less than about 5 atomic percent, the recording layer having a coercivity H c greater than about 6000 Oe and a nucleation field H n more negative than about −2000 Oe.