Patent ID: 7289293

Claim:
A perpendicular recording magnetic disk apparatus comprising: a perpendicular two-layered medium comprising a pinning layer, a soft underlayer and a perpendicular recording layer; and a write head comprising a main pole, a return yoke and an exciting coil, wherein, given that T w is a track width (in μm) of the main pole, PT is a dimension (in μm) in a head tracking direction of the main pole, B (T) is a saturation flux density of the main pole, and t is a thickness (in nm) of the soft underlayer, a magnetization recoverable magnetic field H exf satisfies a relationship represented by the following formula: H exf >(((0.264*log( t )+2.77)* B −0.09)*exp(3.48 *PT*T w ))*(201*exp(−0.014 *t )).