Patent ID: 7799445

Claim:
A perpendicular magnetic recording medium comprising: an anti-ferromagnetic layer; a first soft magnetic underlayer formed on the anti-ferromagnetic layer; a non-magnetic layer formed on the first soft magnetic underlayer; a second soft magnetic underlayer formed on the non-magnetic layer; and a recording layer formed on the second soft magnetic underlayer, wherein the second soft magnetic underlayer is magnetized in a direction opposite to a direction along which the first soft magnetic underlayer is magnetized, and wherein a ratio of M s t of the second soft magnetic underlayer to M s t of the first soft magnetic underlayer is approximately 0.4 to 0.8, where M s is a saturation magnetization value, t is a thickness value, and M s of a material forming the first soft magnetic underlayer or the second soft magnetic underlayer is approximately 1000 to 1500 emu/cc.