Magnetic recording medium exhibiting low noise and high coercive force
View Patent ↗A magnetic recording medium exhibiting low noise and having a sufficiently high coercive force includes a magnetic layer having a granular structure including ferromagnetic crystal grains with a hexagonal closed packed structure and a nonmagnetic grain boundary region of mainly an oxide intervening between the crystal grains. An underlayer has a body-centered cubic lattice structure. A nonmagnetic intermediate layer with the hexagonal closest packed structure includes Ru, Os, and/or Re, which are provided between the magnetic layer and the underlayer. A degree of mismatching Δ=|d 1 −d 2 |/d 1 is at most 10%, for instance, in a range from 2.5% to 7.0%, where d 1 is a spacing of lattice planes of the crystal grains in the magnetic layer and d 2 is a spacing of the lattice planes of the crystal grains in the intermediate layer. A proportion of the crystal grains with a grain size of equal or greater than 8 nm are at most 10% of the crystal grains included in the intermediate layer and a standard deviation of the grain size is at most 1.4 nm. The layers are deposited without preheating the substrate.
1. A magnetic recording medium, comprising:
a substrate;
a nonmagnetic underlayer;
a nonmagnetic intermediate layer;
a magnetic layer;
a protective layer; and
a lubricant film,
wherein the magnetic layer has a granular structure comprising ferromagnetic crystal grains with a hexagonal closed packed structure and a nonmagnetic grain boundary region of an oxide intervening between the ferromagnetic crystal grains,
the nonmagnetic underlayer has a body-centered cubic lattice structure,
the nonmagnetic underlayer, the nonmagnetic intermediate layer, the magnetic layer, the protective layer, and the lubricant film are sequentially laminated on the substrate,
the nonmagnetic intermediate layer is a nonmagnetic metal comprising Ru, Os, and/or Re,
a degree of mismatching Δ=|d 1 −d 2 |/d 1 is at most 10%, where d 1 is a spacing of lattice planes of crystal grains in the magnetic layer and d 2 is a spacing of lattice planes of crystal grains in the nonmagnetic intermediate layer, and
a proportion of the crystal grains in the nonmagnetic intermediate layer with respect to a grain size of equal to or greater than 8 nm is at most 10% of the crystal grains in the nonmagnetic intermediate layer and a standard deviation of said grain size is at most 1.4 nm.
2. A magnetic recording medium, comprising:
a substrate;
a nonmagnetic underlayer;
a magnetic layer;
a protective layer;
a lubricant film,
wherein the magnetic layer has a granular structure comprising ferromagnetic crystal grains with a hexagonal closed packed structure and a nonmagnetic grain boundary region of an oxide intervening between the ferromagnetic crystal grains,
the underlayer has a body-centered cubic lattice structure, and
the nonmagnetic underlayer, the magnetic layer, the protective layer, and the lubricant film are sequentially laminated on the substrate,
a nonmagnetic intermediate layer with a hexagonal closed packed structure disposed between the magnetic layer and the underlayer, the nonmagnetic intermediate layer being a nonmagnetic metal comprising Ru, Os, and/or Re,
a degree of mismatching Δ=|d 1 −d 2 |/d 1 is at most 10%, where d 1 is a spacing of lattice planes of crystal grains in the magnetic layer and d 2 is a spacing of lattice planes of crystal grains in the nonmagnetic intermediate layer, and
a proportion of the crystal grains in the nonmagnetic intermediate layer with respect to a grain size of equal to or greater than 8 nm is at most 10% of the crystal grains in the nonmagnetic intermediate layer and a standard deviation of said grain size is at most 1.4 nm.
3. The magnetic recording medium as recited in claim 2 , wherein the substrate is not subjected to an intentional heating prior to depositing the layers.
4. The magnetic recording medium as recited in claim 2 , wherein the substrate is a resin substrate.
5. The magnetic recording medium as recited in claim 2 , wherein the substrate is not subjected to an intentional heating prior to depositing the layers.
6. The magnetic recording medium as recited in claim 2 , wherein the substrate is a resin substrate.
7. The magnetic recording medium as recited in claim 2 , wherein the degree of mismatching Δ is in a range from 2.5% to 7.0%.
8. The magnetic recording medium as recited in claim 1 , wherein the ferromagnetic crystal grains comprise 12 at % to 20 at % of platinum.
9. The magnetic recording medium as recited in claim 1 , wherein the substrate is not subjected to an intentional heating prior to depositing the layers.
10. The magnetic recording medium as recited in claim 9 , wherein the substrate is a resin substrate.
11. The magnetic recording medium as recited in claim 1 , wherein the substrate is a resin substrate.
12. A magnetic recording medium, comprising:
a substrate;
a nonmagnetic underlayer having a body-centered cubic lattice structure;
a nonmagnetic intermediate layer having a hexagonal closed packed structure;
a magnetic layer having a granular structure including ferromagnetic crystal grains with a hexagonal closed packed structure and a nonmagnetic grain boundary region of an oxide intervening between the ferromagnetic crystal grains;
a protective layer; and
a lubricant film,
wherein the nonmagnetic underlayer, the nonmagnetic intermediate layer, the magnetic layer, the protective layer, and the lubricant film are contiguous and respectively sequentially laminated on the substrate,
the nonmagnetic intermediate layer is a nonmagnetic metal comprising Ru, Os, and/or Re,
a degree of mismatching Δ=|d 1 −d 2 |/d 1 is at most 10%, where d 1 is a spacing of lattice planes of crystal grains in the magnetic layer and d 2 is a spacing of lattice planes of crystal grains in the nonmagnetic intermediate layer, and
a proportion of the crystal grains in the nonmagnetic intermediate layer with respect to a grain size of equal to or greater than 8 nm is at most 10% of the crystal grains in the nonmagnetic intermediate layer and a standard deviation of said grain size is at most 1.4 nm.
13. A magnetic recording medium, comprising:
a nonmagnetic underlayer having a body-centered cubic lattice structure;
a nonmagnetic intermediate layer; and
a magnetic layer having a granular structure including ferromagnetic crystal grains with a hexagonal closed packed structure and a nonmagnetic grain boundary region of an oxide intervening between the ferromagnetic crystal grains,
wherein the nonmagnetic layer underlayer, the nonmagnetic intermediate layer, and the magnetic layer are positioned sequentially,
the nonmagnetic intermediate layer is a nonmagnetic metal comprising Ru, Os, and/or Re, wherein a degree of mismatching Δ=|d 1 −d 2 |/d 1 is at most 10%, where d 1 is a spacing of lattice planes of crystal grains in the magnetic layer and d 2 is a spacing of lattice planes of crystal grains in the nonmagnetic intermediate layer, and
a proportion of the crystal grains in the nonmagnetic intermediate layer with respect to a grain size of equal to or greater than 8 nm is at most 10% of the crystal grains in the nonmagnetic intermediate layer and a standard deviation of said grain size is at most 1.4 nm.
14. The magnetic recording medium as recited in claim 13 , wherein the crystal grains in the magnetic layer grow epitaxially from the interface with the nonmagnetic intermediate layer.