Magnetic recording medium and magnetic storage apparatus

• US 20040013910A1
• Filed: 05/22/2003
• Published: 01/22/2004
• Est. Priority Date: 11/29/2000
• Status: Active Grant

• Current Assignee: Showa Denko KK
• Original Assignee: Fujitsu Limited
• Inventors: Acharya, B. Ramamurthy, Abarra, E. Noel
• Granted Patent: US 6,893,735 B2
• Time in Patent Office: Days
• US Class Current: 428/694ST
• CPC Class Codes: G11B 2005/0002 Special dispositions or recording techniques
• CPC Class Codes: G11B 2005/0005 Arrangements, methods or circuits
• CPC Class Codes: G11B 5/00 Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor G11B11/00 and G11B13/00 take precedence
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/656 containing Co containing inorganic, non-oxide compounds of Si, N, P, B, H or C G11B5/657; containing oxygen G11B5/658
• CPC Class Codes: G11B 5/66 the record carriers consisting of several layers
• CPC Class Codes: G11B 5/672 having different compositions in a plurality of magnetic layers, e.g. layer compositions having differing elemental components or differing proportions of elements
• CPC Class Codes: G11B 5/678 having three or more magnetic layers
• CPC Class Codes: G11B 5/74 Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
• CPC Class Codes: G11B 5/82 Disk carriers
• CPC Class Codes: Y10T 428/12465 having magnetic properties, or preformed fiber orientation coordinate with shape
• CPC Class Codes: Y10T 428/12861 Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/12868 Group IB metal-base component alternative to platinum group metal-base component [e.g., precious metal, etc.]
• CPC Class Codes: Y10T 428/12931 Co-, Fe-, or Ni-base components, alternative to each other

Abstract

A magnetic recording medium includes a nonmagnetic underlayer, an initial magnetic layer, a nonmagnetic spacer layer provided on the initial magnetic layer, and a final magnetic layer provided on the nonmagnetic spacer layer. The initial magnetic layer is disposed closer to the nonmagnetic underlayer than the final magnetic layer, and the initial and final magnetic layers are made of mutually different compositions and are anti-ferromagnetically coupled.

Claims

1. A magnetic recording medium comprising:

a nonmagnetic underlayer;

an initial magnetic layer;

a nonmagnetic spacer layer provided on the initial magnetic layer; and

a final magnetic layer provided on the nonmagnetic spacer layer,

said initial magnetic layer being disposed closer to said nonmagnetic underlayer than said final magnetic layer,

said initial and final magnetic layers being made of mutually different compositions and being anti-ferromagnetically coupled.

2. The magnetic recording medium as claimed in claim 1, wherein said initial and final magnetic layers satisfy a relationship Msi≠

Msf, where Msi denotes a saturation magnetization of the initial magnetic layer and Msf denotes a saturation magnetization of the final magnetic layer.

3. The magnetic recording medium as claimed in claim 1, wherein said initial and final magnetic layers satisfy a relationship Hci≠

Hcf, where Hci denotes a coercivity of the initial magnetic layer and Hcf denotes a coercivity of the final magnetic layer.

6. The magnetic recording medium as claimed in any of claims 1 to 5, wherein more than one pair of the initial magnetic layer, the nonmagnetic spacer layer and the final magnetic layer are provided with a spacer magnetic layer disposed between such pairs.

7. The magnetic recording medium as claimed in any of claims 1 to 6, wherein said initial and final magnetic layers are made of a material selected from a group of CoCrTa, CoCrPt, CoCrPtB, CoCrPtTa, CoCrPtBCu, CoCrPtBAg, CoCrPtBRe, CoCrPtAu, CoCrPtW, CoCrPtTaNb, and alloys thereof.

8. The magnetic recording medium as claimed in any of claims 1 to 7, wherein said nonmagnetic spacer layer is made of a material selected from a group of Ru, Ir, Rh and alloys thereof.

19. A magnetic storage apparatus comprising at least one magnetic recording medium recited in one of claims 1 to 18.

4. A magnetic recording medium comprising:

a nonmagnetic underlayer;

an initial magnetic layer;

a nonmagnetic spacer layer provided on the initial magnetic layer; and

a final magnetic layer provided on the nonmagnetic spacer layer,

said initial magnetic layer being disposed closer to said nonmagnetic underlayer than said final magnetic layer,

said initial and final magnetic layers being anti-ferromagnetically coupled, and satisfying a relationship Msi<

Msf, where Msi denotes a saturation magnetization of the initial magnetic layer and Msf denotes a saturation magnetization of the final magnetic layer.

5. A magnetic recording medium comprising:

a nonmagnetic underlayer;

an initial magnetic layer;

a nonmagnetic spacer layer provided on the initial magnetic layer; and

a final magnetic layer provided on the nonmagnetic spacer layer,

said initial magnetic layer being disposed closer to said nonmagnetic underlayer than said final magnetic layer,

said initial and final magnetic layers being anti-ferromagnetically coupled, and satisfying a relationship Hci<

Hcf, where Hci denotes a coercivity of the initial magnetic layer and Hcf denotes a coercivity of the final magnetic layer.

9. A magnetic recording medium comprising:

a nonmagnetic underlayer;

an initial magnetic layer;

a nonmagnetic spacer layer provided on the initial magnetic layer;

a middle magnetic layer provided on the nonmagnetic spacer layer; and

a final magnetic layer provided on the middle magnetic layer,

said initial magnetic layer being disposed closer to said nonmagnetic underlayer than said middle and final magnetic layers,

said initial and middle magnetic layers being anti-ferromagnetically coupled,

said middle and final magnetic layers being ferromagnetically coupled,

at least two of said initial, middle and final magnetic layers being made of mutually different compositions.

10. The magnetic recording medium as claimed in claim 9, wherein said initial, middle and final magnetic layers satisfy at least two of relationships Msi≠

Msm, Msm≠

Msf and Msi≠

Msf where Msi denotes a saturation magnetization of the initial magnetic layer, Msm denotes a saturation magnetization of the middle magnetic layer and Msf denotes a saturation magnetization of the final magnetic layer.

11. The magnetic recording medium as claimed in claim 9, wherein said initial, middle and final magnetic layers satisfy at least two of relationships Hci≠

Hcm, Hcm≠

Hcf and Hci≠

Hcf where Hci denotes a coercivity of the initial magnetic layer, Hcm denotes a coercivity of the middle magnetic layer and Hcf denotes a coercivity of the final magnetic layer.

14. The magnetic recording medium as claimed in any of claims 9 to 13, wherein more than one pair of the initial magnetic layer, the nonmagnetic spacer layer, the middle magnetic layer and the final magnetic layer are provided with a spacer magnetic layer disposed between such pairs.

15. The magnetic recording medium as claimed in any of claims 9 to 14, wherein said initial and middle magnetic layers are made of a CoCr_x1-based alloy, where 15<

x1<

27, and said final magnetic layer is made of a CoCr_y1-based alloy, where 10<

y1<

24.

16. The magnetic recording medium as claimed in any of claims 9 to 14, wherein said initial and middle magnetic layers are made of a CoCrB_x2-based alloy, where 1<

x2<

15, and said final magnetic layer is made of a CoCrB_y2-based alloy, where 0≦

y2<

10.

17. The magnetic recording medium as claimed in any of claims 9 to 14, wherein said initial and final magnetic layers are made of a material selected from a group of CoCrTa, CoCrPt, CoCrPtB, CoCrPtTa, CoCrPtBCu, CoCrPtBAg, CoCrPtBRe, CoCrPtAu, CoCrPtW, CoCrPtTaNb, and alloys thereof.

18. The magnetic recording medium as claimed in any of claims 9 to 17, wherein said nonmagnetic spacer layer is made of a material selected from a group of Ru, Ir, Rh and alloys thereof.

12. A magnetic recording medium comprising:

a nonmagnetic underlayer;

an initial magnetic layer;

a nonmagnetic spacer layer provided on the initial magnetic layer;

a middle magnetic layer provided on the nonmagnetic spacer layer; and

a final magnetic layer provided on the middle magnetic layer,

said initial magnetic layer being disposed closer to said nonmagnetic underlayer than said middle and final magnetic layers,

said initial and middle magnetic layers being anti-ferromagnetically coupled,

said middle and final magnetic layers being ferromagnetically coupled,

said initial, middle and final magnetic layers satisfying a relationship Msi≦

Msm<

Msf, where Msi denotes a saturation magnetization of the initial magnetic layer, Msm denotes a saturation magnetization of the middle magnetic layer and Msf denotes a saturation magnetization of the final magnetic layer.

13. A magnetic recording medium comprising:

a nonmagnetic underlayer;

an initial magnetic layer;

a nonmagnetic spacer layer provided on the initial magnetic layer;

a middle magnetic layer provided on the nonmagnetic spacer layer; and

a final magnetic layer provided on the middle magnetic layer,

said initial magnetic layer being disposed closer to said nonmagnetic underlayer than said middle and final magnetic layers,

said initial and middle magnetic layers being anti-ferromagnetically coupled,

said middle and final magnetic layers being ferromagnetically coupled,

said initial and final magnetic layers being anti-ferromagnetically coupled, and satisfying a relationship Hci≦

Hcm<

Hcf, where Hci denotes a coercivity of the initial magnetic layer, Hcm denotes a coercivity of the middle magnetic layer and Hcf denotes a coercivity of the final magnetic layer.