Base for magnetic recording medium, and HDD
A base for a magnetic recording medium, includes a substrate made of an Al alloy and having a surface, and a film made of a NiWP-based alloy and plated on the surface of the substrate. The film includes W in a range of 15 mass % to 22 mass %, P in a range of 3 mass % to 10 mass %, and Pb in a range of 0.03 mass % to 0.08 mass %. The film has a thickness of 5 μm or greater.
1. A base for a magnetic recording medium, comprising:
a substrate made of an Al alloy and having a surface; and
a film made of a NiWP-based alloy and plated on the surface of the substrate,
wherein the film includes W in a range of 15 mass % to 22 mass %, P in a range of 3 mass % to 10 mass %, and Pb in a range of 0.03 mass % to 0.08 mass %, and
wherein the film has a thickness of 5 μm or greater.
2. The base for the magnetic recording medium as claimed in claim 1 , wherein the substrate includes Mg in a range of 2 mass % to 7 mass %, and Cr in a range of 0.02 mass % to 0.3 mass %.
3. The base for the magnetic recording medium as claimed in claim 1 , further comprising:
a magnetic layer, provided above the surface of the substrate, and made of a L1 0 type FePt alloy having a L1 0 type crystal structure, or a L1 0 type CoPt alloy having a L1 0 type crystal structure.
4. The base for the magnetic recording medium as claimed in claim 1 , having an outer diameter of 53 mm or greater, a thickness of 0.9 mm or less, and a Young's modulus of 79 GPa or higher.
5. The base for the magnetic recording medium as claimed in claim 1 ,
wherein a plurality of cavities are formed at the surface of the substrate after heating the substrate at 400° C. for 2 hours, and
wherein a surface density of cavities having a depth of 5 nm or greater from the surface of the substrate is 100 cavities/mm 2 .
6. The base for the magnetic recording medium as claimed in claim 5 , wherein the substrate includes Mg in a range of 2 mass % to 7 mass %, and Cr in a range of 0.02 mass % to 0.3 mass %.
7. The base for the magnetic recording medium as claimed in claim 5 , further comprising:
a magnetic layer, provided above the surface of the substrate, and made of a L1 0 type FePt alloy having a L1 0 type crystal structure, or a L1 0 type CoPt alloy having a L1 0 type crystal structure.
8. The base for the magnetic recording medium as claimed in claim 5 , having an outer diameter of 53 mm or greater, a thickness of 0.9 mm or less, and a Young's modulus of 79 GPa or higher.
9. The base for the magnetic recording medium as claimed in claim 1 , wherein a warp of the substrate after heating the substrate at 450° C. for 2 minutes is 20 μm or less.
10. The base for the magnetic recording medium as claimed in claim 9 , wherein the substrate includes Mg in a range of 2 mass % to 7 mass %, and Cr in a range of 0.02 mass % to 0.3 mass %.
11. The base for the magnetic recording medium as claimed in claim 9 , further comprising:
a magnetic layer, provided above the surface of the substrate, and made of a L1 0 type FePt alloy having a L1 0 type crystal structure, or a L1 0 type CoPt alloy having a L1 0 type crystal structure.
12. The base for the magnetic recording medium as claimed in claim 9 , having an outer diameter of 53 mm or greater, a thickness of 0.9 mm or less, and a Young's modulus of 79 GPa or higher.
13. A 3.5-inch standardized hard disk drive comprising:
a plurality of magnetic disks;
a plurality of heads configured to write information to and read information from the plurality of magnetic disks; and
a casing configured to accommodate the plurality of magnetic disks and the plurality of heads,
wherein each of the plurality of disks, forming a magnetic recording medium, includes:
the base for the magnetic recording medium according to claim 1 ; and
a magnetic layer provided above the surface of the substrate.
14. The 3.5-inch standardized hard disk drive as claimed in claim 13 , wherein the substrate of each of the plurality of magnetic disks includes Mg in a range of 2 mass % to 7 mass %, and Cr in a range of 0.02 mass % to 0.3 mass %.
15. The 3.5-inch standardized hard disk drive as claimed in claim 13 , wherein the magnetic layer of each of the plurality of magnetic disks is made of a L1 0 type FePt alloy having a L1 0 type crystal structure, or a L1 0 type CoPt alloy having a L1 0 type crystal structure.
16. The 3.5-inch standardized hard disk drive as claimed in claim 13 , wherein each of the plurality of magnetic disks has a thickness of 0.9 min or less, and a Young's modulus of 79 GPa or higher.
17. The 3.5-inch standardized hard disk drive as claimed in claim 13 ,
wherein a plurality of cavities are formed at the surface of the substrate of each of the plurality of magnetic disks after heating the substrate at 400° C. for 2 hours, and
wherein a surface density of cavities having a depth of 5 nm or greater from the surface of the substrate of each of the plurality of magnetic disks is 100 cavities/mm 2 .
18. The 3.5-inch standardized hard disk drive as claimed in claim 13 , wherein a warp of the substrate of each of the plurality of magnetic disks after heating the substrate of each of the plurality of magnetic disks at 450° C. for 2 minutes is 20 μm or less.
19. A magnetic recording medium comprising:
the base for the magnetic recording medium according to claim 1 ; and
a magnetic layer, provided above the surface of the substrate that has a disk shape,
wherein the magnetic layer is made of a L1 0 type FePt alloy having a L1 0 type crystal structure, or a L1 0 type CoPt alloy having a L1 0 type crystal structure.
20. A hard disk drive comprising:
the magnetic recording medium according to claim 19 and having a disk shape;
a head configured to write information to and read information from the magnetic recording medium; and
a casing configured to accommodate the magnetic recording medium and the head.