Patent ID: 7976965
Filing Date: 2011-07-12
Classification: G11B

Abstract:
1. A magnetic recording medium comprising a nonmagnetic substrate on which at least a soft magnetic under layer, an orientation adjusting layer that controls the orientation of a layer just thereon, a vertical magnetic layer with an axis of easy magnetization being mainly oriented vertically to the nonmagnetic substrate and a protective layer are disposed, the vertical magnetic layer being constituted of three or more layers including a lower layer, an intermediate layer and an upper layer from the substrate side, wherein the lower, intermediate and upper magnetic layers are constituted of magnetic particles which are columnar crystals extending continuously from the lower layer to the upper layer such that the magnetic particles epitaxially extend one-on-one from each magnetic layer to the other magnetic layers, the magnetic recording medium further comprising a nonmagnetic layer between the lower and intermediate magnetic layers or between the intermediate and upper magnetic layers, wherein the upper layer has a magnetic anisotropic constant (Ku) ranging from 0.8×10 wherein the Kus of said upper, intermediate and lower magnetic layers have the following relation: Ku of the upper layer<Ku of the lower layer<Ku of the intermediate layer, and wherein said lower and intermediate magnetic layers are magnetic layers having a granular structure in which the surrounding of the columnar magnetic particle is coated with an oxide and said upper magnetic layer is a magnetic layer containing no oxide.