Perpendicular magnetic recording medium utilizing a first cobalt magnetic layer and a second Pd-SiO
View Patent ↗A perpendicular magnetic recording medium is disclosed that exhibits reduced media noise and enhanced thermal stability of recorded magnetization, and thus provides a medium of high recording density and excellent read-write performance. The perpendicular magnetic recording medium comprises a magnetic film on a nonmagnetic substrate. The magnetic film is a multilayered lamination film composed of alternately laminated first magnetic layers of cobalt and second magnetic layers of palladium, the second magnetic layers containing SiO 2 . By setting a ratio of Ku 2 to Ku to a value not smaller than a specified value, the compatibility between the ease of writing-in to the perpendicular magnetic recording medium by a head and the thermal stability of recorded magnetization is more improved.
1. A perpendicular magnetic recording medium comprising a magnetic film formed on a nonmagnetic substrate, wherein the magnetic film is multilayered and comprises alternately laminated first magnetic layers of cobalt containing no additive and second layers of palladium, the second layers containing silicon oxide, wherein crystalline magnetic anisotropy energy of the magnetic trim is approximated by E≈Ku 1 sin 2 θ+Ku 2 sin 4 θ, where Ku 1 and Ku 2 are uniaxial anisotropy constants, θ is an angle between spontaneous magnetization and an axis of easy magnetization of the magnetic film, and a crystalline magnetic anisotropy constant Ku, where Ku=Ku 1 +Ku 2 , and the Ku and the Ku 2 obtained by magnetic anisotropy measurement using a torque magnetization meter under a condition of approximately saturated magnetization of the magnetic film satisfies Ku 2 /Ku≧0.25.
2. The perpendicular magnetic recording medium according to claim 1 , wherein the amount of added silicon oxide is in the concentration range of 2 to 8 mol %.
3. The perpendicular magnetic recording medium according to claim 1 , wherein a thickness of the first magnetic layer is in the range of 0.2 to 0.5 nm and a thickness of the second layer is in the range of 0.6 to 1.0 nm.
4. The perpendicular magnetic recording medium according to claim 3 , wherein the backing layer is composed of an alloy of CoZrNb or CoZrTa, and has a thickness in the range of 50 to 300 nm.
5. The perpendicular magnetic recording medium according to claim 1 , wherein an underlayer is provided between the magnetic film and the substrate, and the magnetic film is provided directly on the underlayer.
6. The perpendicular magnetic recording medium according to claim 5 , wherein the underlayer is a ruthenium film.
7. The perpendicular magnetic recording medium according to claim 5 , wherein a thickness of the underlayer is in the range of 5 to 20 nm.
8. The perpendicular magnetic recording medium according claim 5 , wherein a surface of the underlayer is adsorbed with oxygen.
9. The perpendicular magnetic recording medium according to claim 5 , wherein an alignment control layer is provided between the substrate and the underlayer for C-axis alignment of crystal alignment of the underlayer.
10. The perpendicular magnetic recording medium according to claim 9 , wherein the alignment control layer is composed by laminating a first alignment control layer and a second alignment control layer.
11. The perpendicular magnetic recording medium according to claim 10 , wherein the first alignment control layer is a tantalum layer and the second alignment control layer is selected from a NiFeNbB layer, a NiFeCr layer, and a NiFeSi layer.
12. The perpendicular magnetic recording medium according to claim 11 , wherein a composition of the NiFeNbB layer is in the range of 64 to 86 at % Ni, 10 to 20 at % Fe, 2 to 10 at % Nb, and 2 to 6 at % B wherein the sum of the atom percentages of Ni, Fe, Nb and B is 100 at %; a composition of the NiFeCr layer is in the range of 50 to 70 at % Ni, 10 to 20 at % Fe, and 20 to 30 at % Cr wherein the sum of the atom percentages of Ni, Fe, and Cr is 100 at %; a composition of the NiFeSi layer is in the range of 70 to 88 at % Ni, 10 to 20 at % Fe, and 2 to 10 at % Si wherein the sum of the atom percentages of Ni, Fe, and Si is 100 at %.
13. The perpendicular magnetic recording medium according to claim 10 , wherein a thickness of the first alignment control layer is in the range of 1 to 5 nm and a thickness of the second alignment control layer is in the range of 5 to 30 nm.
14. The perpendicular magnetic recording medium according to claim 10 , wherein a soft magnetic backing layer is provided between the substrate and the first alignment control layer.
15. A method of manufacturing a perpendicular magnetic recording medium, the method comprising:
depositing an underlayer of a ruthenium film on a nonmagnetic substrate, and
depositing a magnetic film of multilayered lamination film directly on the underlayer by alternately laminating first magnetic layers of cobalt containing no additive and second layers of palladium containing silicon oxide, wherein crystalline magnetic anisotropy energy of the magnetic trim is approximated by E≈Ku 1 sin 2 θ+Ku 2 sin 4 θ, where Ku 1 and Ku 2 are uniaxial anisotropy constants, θ is an angle between spontaneous magnetization and an axis of easy magnetization of the magnetic film, and a crystalline magnetic anisotropy constant Ku, where Ku=Ku 1 +Ku 2 , and the Ku and the Ku 2 obtained by magnetic anisotropy measurement using a torque magnetization meter under a condition of approximately saturated magnetization of the magnetic film satisfies Ku 2 /Ku≧0.25.
16. The method of manufacturing a perpendicular magnetic recording medium according to claim 15 , wherein depositing the magnetic film is conducted by a sputtering method using a target of cobalt and a target of palladium containing silicon oxide in a concentration range of 2 to 8 mol %.
17. The method of manufacturing a perpendicular magnetic recording medium according to claim 15 , wherein, during depositing of the underlayer, oxygen is adsorbed on a surface of the underlayer by exposing the surface of the underlayer to argon gas at a gas pressure in the range of 0.1 to 10 Pa containing oxygen in the mass flow range of 1 to 10% for a time duration in the range of 1 to 10 sec.
18. The method of manufacturing a perpendicular magnetic recording medium according to claim 15 , further comprising depositing an alignment control layer prior to depositing of the underlayer, said alignment control layer comprising a first alignment control layer of tantalum and a second alignment control layer selected from a NiFeNbB layer, a NiFeCr layer, and a NiFeSi layer and producing crystal alignment of the underlayer in C-axis alignment, wherein the first alignment control layer and the second alignment control layer are laminated during deposition.
19. The method of manufacturing a perpendicular magnetic recording medium according to claim 15 , further comprising depositing a backing layer in which a soft magnetic backing layer of a CoZrNb layer or a CoZrTa layer is deposited on the substrate prior to depositing the alignment control layer.