Patent ID: 8367229
Filing Date: 2013-02-05
Classification: G11B

Abstract:
1. A perpendicular magnetic recording medium comprising a nonmagnetic substrate, and at least a soft magnetic layer (SUL), an alignment control layer, a magnetic recording layer and a protective layer formed on the nonmagnetic substrate; wherein the magnetic recording layer is constituted of two or more layers and includes a first magnetic recording layer and a second magnetic recording layer from the nonmagnetic substrate side and, regarding magnetocrystalline anisotropic energy Ku of each magnetic recording layer, the first magnetic recording layer has 4×10 and the second magnetic recording layer has 2×10 wherein the first magnetic recording layer is constituted of CoCrPtRu magnetic alloy crystal grains and grain boundaries made of an oxide, wherein the first magnetic recording layer contains 3 to 8 atomic % of at least one element selected from the group consisting of Al, V, Ti, Mo, Nb, Zr, W, Ta, Hf, Re, Gd, Tb, Sm, Ce, Nd and Pr in CoCrPtRu magnetic alloy crystal grains, and the area of grain boundaries is 30% to 35% based on the entire area in a planar TEM observation of the first magnetic recording layer.