Patent ID: 9064518
Filing Date: 2015-06-23
Classification: G11B

Abstract:
1. A perpendicular magnetic recording medium, comprising: a base; a first magnetic layer having a granular structure in which a non-magnetic grain boundary portion is formed between crystal particles grown in a columnar shape; a non-magnetic split layer containing (1) at least one of Ru and an Ru alloy and (2) an oxide, and being disposed directly on the first magnetic layer; and a second magnetic layer that is disposed directly on the split layer and that has a granular structure in which a non-magnetic grain boundary portion is formed between crystal particles grown in a columnar shape, wherein the first magnetic layer and the second magnetic layer contain oxides which form the grain boundary portion, and when an oxide content of the first magnetic layer is represented by A and an oxide content of the second magnetic layer is represented by B, a relationship between the oxide contents A/B is in the range of 0.7<A/B<0.9, wherein the split layer is a single coating film in a range of 2 Å to 10 Å in film thickness, has no grain boundaries, and is operative to interrupt magnetism between the first magnetic layer and the second magnetic layer to generate antiferro-magnetic exchange coupling, wherein the first magnetic layer is in a range of 0.7 nm to 3.0 nm in film thickness, and wherein the first magnetic layer and second magnetic layer are different in composition and thickness from each other, whereby said medium has a Hc of 4900 Oe or more and a SNR of 17.7 dB or more.