Magnetic recording medium, method of manufacturing the same, and magnetic recording/reproduction apparatus

A magnetic recording medium manufacturing method comprising:

• forming, on a nonmagnetic substrate, a nonmagnetic underlayer containing ruthenium and at least one element selected from the group consisting of chromium, titanium, and silicon;
• forming a magnetic recording layer containing platinum and at least one of iron and cobalt, such that the magnetic recording layer is in contact with the nonmagnetic underlayer;
• forming, on the perpendicular magnetic recording layer, a mask layer having patterns regularly arranged in a longitudinal direction;
• and
• performing gas ion irradiation by using one of nitrogen gas and a gas mixture of nitrogen gas and at least one gas selected from the group consisting of helium, hydrogen, and B2H6,
• thereby forming a recording portion having regularly arranged patterns and a demagnetized non-recording portion in the magnetic recording layer by demagnetizing a region not covered with the mask layer by mixing the magnetic recording layer and the nonmagnetic underlayer in the region in a thickness direction.

A magnetic recording/reproduction apparatus comprising:

• a perpendicular magnetic recording medium comprising a nonmagnetic underlayer and a perpendicular magnetic recording layer stacked on a nonmagnetic substrate, wherein the nonmagnetic underlayer contains ruthenium and at least one element selected from the group consisting of chromium, titanium, and silicon, and wherein the perpendicular magnetic recording layer is formed in contact with the nonmagnetic underlayer and contains platinum and at least one of iron and cobalt;
• and
• a mask layer formed on the perpendicular magnetic recording layer, the mask layer having patterns regularly arranged in a longitudinal direction,
• wherein gas ion irradiation is performed using one of nitrogen gas and a gas mixture of nitrogen gas and at least one gas selected from the group consisting of helium, hydrogen, and B2H6, thereby forming a non-recording portion in a region of the perpendicular magnetic recording layer which is not covered with the mask layer by demagnetizing the region by mixing at least some components of the perpendicular magnetic recording layer and some components of the nonmagnetic underlayer in a thickness direction, the non-recording portion containing nitrogen, at least one of iron and cobalt, and at least one element selected from the group consisting of platinum, chromium, titanium, and silicon, and thereby forming a recording portion containing platinum and at least one of iron and cobalt in a region of the perpendicular magnetic recording layer which is covered with the mask layer;
• a mechanism configured to support and rotate the perpendicular magnetic recording medium;
• a magnetic head comprising an element configured to record information on the perpendicular magnetic recording medium, and an element configured to reproduce recorded information;
• and
• a carriage assembly configured to support the magnetic head such that the magnetic head freely moves with respect to the perpendicular magnetic recording medium.