Heat-assisted magnetic recording medium and magnetic storage apparatus

A magnetic storage apparatus comprising:

• a heat-assisted magnetic recording medium;
• a magnetic head configured to write information to and read information from the heat-assisted magnetic recording medium;
• and
• a casing configured to accommodate the heat-assisted magnetic recording medium and the magnetic head,
• wherein the magnetic head includes a laser light generator configured to generate laser light, a waveguide configured to guide the laser light to a tip end of the magnetic head, and a near-field light generator configured to generate near-field light which heats the magnetic recording medium,
• wherein the heat-assisted magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L10 crystal structure, which are arranged in this order,
• wherein the magnetic layer includes a first magnetic layer, and a second magnetic layer which is arranged farther away from the substrate than the first magnetic layer,
• wherein each of the first magnetic layer and the second magnetic layer has a granular structure including C, SiO2, and BN at grain boundaries,
• wherein a volume fraction of the grain boundaries in each of the first magnetic layer and the second magnetic layer is within a range of 25 vol % to 45 vol %,
• wherein a volume fraction of C in the first magnetic layer is within a range of 5 vol % to 22 vol %,
• wherein a volume ratio of SiO2 with respect to BN in each of the first magnetic layer and the second magnetic layer is within a range of 0.25 to 3.5,
• wherein a volume fraction of SiO2 in the second magnetic layer is greater than a volume fraction of SiO2 in the first magnetic layer by 5 vol % or more, and
• wherein a volume fraction of BN in the second magnetic layer is smaller than a volume fraction of BN in the first magnetic layer by 2 vol % or more.