Patent ID: 6740383
Filing Date: 2004-05-25
Classification: B82Y,G11B,Y10T

Abstract:
A magnetic recording disk comprising a nonmagnetic glass substrate having non-oriented irregularities on a surface thereof, and, having applied thereon in the following order:an underlayer which comprises a first underlayer consisting of chromium and having a thickness of 5 to 25 nm, a second sputtered underlayer consisting of nickel and phosphorus and a third underlayer consisting of chromium and molybdenum which are formed in the described order, wherein said second underlayer has a thickness of not less than 5 nm, contains P in the concentration of 15 to 33 atom % in the NiP layer and has a mechanically textured structure having a surface roughness Ra2 in a radial direction of less than 2 nm, and said third underlayer has a thickness of not more than 60 nm and has a widened lattice spacing approaching the lattice spacing of a magnetic recording layer formed thereon, a magnetic recording layer which has a circumferential direction of easy magnetization and contains cobalt as a principal component thereof, and also contains chromium in an amount of at least 14 at % and platinum in an amount of at least 4 at % in combination with tantalum or tantalum and niobium, and a Hc ratio of a perpendicular coercive force Hc âŠ¥ to a horizontal coercive force Hc // is not more than 0.22.