Patent ID: 6852398
Filing Date: 2005-02-08
Classification: G11B,Y10T

Abstract:
1. Perpendicular magnetic recording media, comprising: a non-magnetic substrate; an underlayer provided on the substrate having predetermined permeability characteristics; a first perpendicular magnetic recording layer provided with perpendicular magnetic anisotropy on the underlayer, which has ferromagnetic grains surrounded with non-magnetic boundaries so that the magnitude of magnetic exchange interaction between the grains is substantially zero; and a second perpendicular magnetic recording layer provided with perpendicular magnetic anisotropy on the first perpendicular magnetic recording layer, which has a polycrystalline structure including ferromagnetic grains wherein boundaries thereof are non-magnetic to make magnetic exchange interaction between grains larger than that in the first perpendicular magnetic recording layer, wherein: an exchange stiffness constant between grains of the first recording layer is 0.05×10