Patent ID: 8252152

Claim:
A method of manufacturing a perpendicular magnetic recording medium, the method comprising the steps of: depositing a nonmagnetic underlayer composed of a metal or an alloy having a hexagonal closest-packed (hcp) crystal structure on a nonmagnetic substrate; depositing a magnetic layer consisting essentially of ferromagnetic crystal grains and a nonmagnetic grain boundary region essentially consisting of an oxide surrounding the ferromagnetic crystal grains by sputtering a composite target containing a ferromagnetic alloy and an oxide on the underlayer in an inert atmosphere, wherein the ferromagnetic crystal grains are composed of an alloy containing at least cobalt and platinum, wherein a volume of the nonmagnetic grain boundary region consisting essentially of the oxide falls within a range of 15% to 40% of a total volume of the magnetic layer, wherein a volume occupied by the oxide contained in the composite target falls within a range of 20% to 35% of a total volume of the composite target, and wherein the volume ratio of the oxide in the magnetic layer formed with the composite target is different from the volume ratio of the oxide in the composite target.