Perpendicular magnetic recording medium with granular structured magnetic recording layer, method for producing the same, and magnetic recording apparatus

A magnetic recording/reproducing apparatus, comprising:

• a magnetic recording medium,
• a medium driving unit that drives the magnetic recording medium,
• a magnetic head that carries out reading/writing of information from/to the magnetic recording medium, and
• a magnetic head access unit that allows the magnetic head to access toward the magnetic recording medium,
• wherein the magnetic recording medium is a perpendicular magnetic recording medium including a substrate, and arranged in order thereon, at least a soft magnetic layer, an intermediate layer, a magnetic recording layer, and a protective layer, wherein the magnetic recording layer has a granular structure composed of a multiplicity of columnar grains and an oxide-containing grain boundary layer, wherein the granular structure is in columnar form in which the columnar grains continuously extend from an interface with the intermediate layer to another interface with the protective layer, and wherein the columnar grains have such shapes that, assuming that the columnar grains are each divided equally into two portions in a film thickness direction thereof, one portion adjacent to the protective layer is larger in diameter than the other portion adjacent to the intermediate layer.

A method for manufacturing a perpendicular magnetic recording medium, the method comprising the steps of:

• forming a soft magnetic layer on a substrate;
• forming an intermediate layer on the soft magnetic layer;
• forming a magnetic recording layer on the intermediate layer, the magnetic recording layer having a granular structure composed of a multiplicity of columnar grains and an oxide-containing grain boundary layer, the granular structure being in columnar form, where the columnar grains continuously extending from an interface with the intermediate layer through the magnetic recording layer, and the columnar grains having such shapes that, assuming that the columnar grains are each divided equally into two portions in a film thickness direction thereof, one portion adjacent to the protective layer is larger in diameter than the other portion adjacent to the intermediate layer,
• wherein the step of forming the magnetic recording layer comprises:
• the first step of forming a first layer of the magnetic recording layer through a sputtering process in which a power P1 is supplied;
• and
• the second step of forming a second layer of the magnetic recording layer through another sputtering process in which a power P2 continuously increased from the power P1 is supplied.

A method for manufacturing a perpendicular magnetic recording medium, the method comprising the steps of:

• forming a soft magnetic layer on a substrate;
• forming an intermediate layer on the soft magnetic layer;
• forming a magnetic recording layer on the intermediate layer, the magnetic recording layer having a granular structure composed of a multiplicity of columnar grains and an oxide-containing grain boundary layer, the granular structure being in columnar form where the columnar grains continuously extending from an interface with the intermediate layer through the magnetic recording layer, and the columnar grains having such shapes that, assuming that the columnar grains are each divided equally into two portions in a film thickness direction thereof, one portion adjacent to the protective layer is larger in diameter than the other portion adjacent to the intermediate layer,
• wherein the step of forming the magnetic recording layer comprises:
• the first step of forming a first layer of the magnetic recording layer through a sputtering process in which an oxygen gas flow rate in a process gas is F1;
• and
• the second step of forming a second layer of the magnetic recording layer through another sputtering process in which an oxygen gas flow rate in the process gas is F2 that is continuously decreased from the oxygen gas flow rate F1.