Perpendicular magnetic recording medium and magnetic storage apparatus using the same

A perpendicular magnetic recording medium having a perpendicular magnetic film formed through an underlayer on a nonmagnetic substrate,

• the underlayer which includes a material having a hexagonal close packed structure or an amorphous structure, comprising:
• a first underlayer nearer to the substrate;
• and
• a second underlayer having a hexagonal close packed structure formed on the first underlayer, a preferred growth orientation of [0001] and a material capable of hetero-epitaxy growth onto the perpendicular magnetic film,
• wherein the perpendicular magnetic film formed on the second underlayer includes a lower perpendicular magnetic layer contacting the second underlayer and an upper perpendicular magnetic layer formed thereon, the perpendicular magnetic film including the lower and upper layers is a Co-alloy polycrystal film, the total concentration of added nonmagnetic elements in the upper perpendicular magnetic layer is lower than that in the lower perpendicular magnetic layer, the saturation magnetization Ms and the magnetic anisotropic energy Ku of the upper perpendicular magnetic layer are larger that those of the lower perpendicular magnetic layer, continuos hetero-epitaxy growth from the second underlayer to the upper perpendicular magnetic layer is made, the total thickness of the perpendicular magnetic film is from 5 to 70 nm, and the average grain size of crystal grains in the upper perpendicular magnetic layer is from 5 to 15 nm on the basis of measurement at the surface side of the upper perpendicular magnetic layer;
• and
• a nonmagnetic layer or a magnetic layer having a saturation magnetization Ms of 50 emu/cc or less is formed as an interlayer between the lower perpendicular magnetic layer and the upper perpendicular magnetic layer, and continuous hetero-epitaxy growth from the second underlayer to the upper perpendicular magnetic layer is made.

A magnetic storage apparatus comprising:

• a magnetic recording medium;
• a spindle motor for rotating the magnetic recording medium;
• a magnetic head having a recording element;
• and
• a reading element, an actuator for positioning the magnetic head, and a means for processing reading/recording signals of the magnetic head,
• wherein the perpendicular magnetic recording medium comprises a perpendicular magnetic film formed through an underlayer on a nonmagnetic substrate,
• the underlayer which includes a material having a hexagonal close packed structure or an amorphous structure, comprises:
• a first underlayer nearer to the substrate;
• and a second underlayer having a hexagonal close packed structure formed on the first underlayer, a preferred growth orientation of [0001] and a material capable of hetero-epitaxy growth onto the perpendicular magnetic film,
• the perpendicular magnetic film formed on the second underlayer includes a lower perpendicular magnetic layer contacting the second underlayer and an upper perpendicular magnetic layer formed thereon, the perpendicular magnetic film including the lower and upper layers is a Co-alloy polycrystal film, the total concentration of added nonmagnetic elements in the upper perpendicular magnetic layer is lower than that in the lower perpendicular magnetic layer, the saturation magnetization Ms and the magnetic anisotropic energy Ku of the upper perpendicular magnetic layer are larger that those of the lower perpendicular magnetic layer, continuos hetero-epitaxy growth from the second underlayer to the upper perpendicular magnetic layer is made, the total thickness of the perpendicular magnetic film is from 5 to 70 nm, and the average grain size of crystal grains in the upper perpendicular magnetic layer is from 5 to 15 nm on the basis of measurement at the surface side of the upper perpendicular magnetic layer.

A magnetic storage apparatus comprising:

• a magnetic recording medium;
• an actuator for rotating and driving the magnetic recording medium;
• a magnetic head for recording and reaching;
• a means for moving the magnetic head relatively to the magnetic recording medium;
• and
• a means for reading output signals from the magnetic head,
• wherein the perpendicular magnetic recording medium has a magnetic recording film having the property of perpendicular easy magnetization and being formed through an underlayer on a nonmagnetic substrate, and a magnetic film or magnetic films having the property of in-plane easy magnetization is/are formed on both surfaces or a single surface of the magnetic recording film.