Heat-assisted magnetic recording medium and magnetic storage apparatus
A heat-assisted magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L1 0 crystal structure and first and second layers, arranged in this order. Each of the first and second layers has a granular structure including C, SiO 2 , and BN at grain boundaries. Vol % of the grain boundaries in each of the first and second layers is 25 to 45 vol %. Vol % of C in the first layer is 5 to 22 vol %, and a volume ratio of SiO 2 with respect to BN in each of the first and second layers is 0.25 to 3.5. Vol % of SiO 2 in the second layer is greater than that of the first layer by 5 vol % or more. Vol % of BN in the second layer is smaller than that in the first layer by 2 vol % or more.
1. A heat-assisted magnetic recording medium comprising:
a substrate, an underlayer, and a magnetic layer including an alloy having a L1 0 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, SiO 2 , 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 SiO 2 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 SiO 2 in the second magnetic layer is greater than a volume fraction of SiO 2 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.
2. The heat-assisted magnetic recording medium as claimed in claim 1 , wherein
each of the first magnetic layer and the second magnetic layer has a thickness of 2 nm or greater, and
the second magnetic layer has a thickness smaller than that of the first magnetic layer.
3. The heat-assisted magnetic recording medium as claimed in claim 2 , wherein the alloy having the L1 0 crystal structure includes one or more metals selected from a group consisting of Rh, Ru, Ir, and Cu, within a range of 2 mol % to 10 mol %.
4. The heat-assisted magnetic recording medium as claimed in claim 1 , wherein the alloy having the L1 0 crystal structure includes one or more metals selected from a group consisting of Rh, Ru, Ir, and Cu, within a range of 2 mol % to 10 mol %.
5. A magnetic storage apparatus comprising:
the heat-assisted magnetic recording medium according to claim 1 ; and
a magnetic head configured to write information to and read information from the heat-assisted magnetic recording medium.
6. 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 L1 0 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, SiO 2 , 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 SiO 2 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 SiO 2 in the second magnetic layer is greater than a volume fraction of SiO 2 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.
7. The magnetic storage apparatus as claimed in claim 6 , wherein
each of the first magnetic layer and the second magnetic layer of the heat-assisted magnetic recording medium has a thickness of 2 nm or greater, and
the second magnetic layer has a thickness smaller than that of the first magnetic layer.
8. The magnetic storage apparatus as claimed in claim 7 , wherein the alloy having the L1 0 crystal structure, included in the magnetic layer of the heat-assisted magnetic recording medium, includes one or more metals selected from a group consisting of Rh, Ru, Ir, and Cu, within a range of 2 mol % to 10 mol %.
9. The magnetic storage apparatus as claimed in claim 6 , wherein the alloy having the L1 0 crystal structure, included in the magnetic layer of the heat-assisted magnetic recording medium, includes one or more metals selected from a group consisting of Rh, Ru, Ir, and Cu, within a range of 2 mol % to 10 mol %.