Anti-ferromagnetically coupled perpendicular magnetic recording media with oxide

• US 20050058855A1
• Filed: 11/01/2004
• Published: 03/17/2005
• Est. Priority Date: 11/30/2001
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Girt, Erol
• Granted Patent: US 7,842,409 B2
• Time in Patent Office: Days
• US Class Current: 428/828
• CPC Class Codes: G11B 5/66 the record carriers consisting of several layers
• CPC Class Codes: G11B 5/676 having magnetic layers separated by a nonmagnetic layer, e.g. antiferromagnetic layer, Cu layer or coupling layer
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

The present invention relates to perpendicular magnetic recording media with improved signal-to-medium noise ratio (“SMNR”) and thermal stability, which media include a pair of vertically spaced-apart perpendicular ferromagnetic layers which are anti-ferromagnetically coupled (“AFC”) across a non-magnetic spacer layer. The invention is of particular utility in the fabrication of data/information storage and retrieval media, e.g., hard disks, having ultra-high areal recording/storage densities.

Claims

1. An anti-ferromagnetically coupled (“

AFC”

) perpendicular magnetic recording medium, comprising;

(a) a non-magnetic substrate having a surface; and

(b) a layer stack formed over said substrate surface, said layer stack comprising, in overlying sequence from said substrate surface;

an underlayer comprised of a magnetically soft ferromagnetic material or a plurality of layers of magnetically soft ferromagnetic material separated by thin non-magnetic spacer layers;

at least one interlayer;

a ferromagnetic stabilization layer with perpendicular anisotropy;

a non-magnetic spacer layer; and

a perpendicularly anisotropic main recording layer comprised of a granular hard ferromagnetic material,

wherein said ferromagnetic stabilization layer and said perpendicularly anisotropic main recording layer are anti-ferromagnetically coupled across said non-magnetic spacer layer.

2. The perpendicular magnetic recording medium as in claim 1, wherein:

said at least one interlayer is selected from one or more of elements selected from the group consisting of Ru, Re, Ir, Cu, Ag, Au, Zr, Hf, Pr, Pd and Ti, containing minor amounts of bcc-structured elements selected from the group consisting of W, Mo, Ta, Nb, Cr and V.

3. The perpendicular magnetic recording medium as in claim 2, wherein:

said at least one interlayer further comprises at least one oxide material containing one or more elements selected from the group consisting of Al, Si, Ti, V, Mn, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf and W.

4. The perpendicular magnetic recording medium as in claim 3, wherein:

said at least one interlayer is from about 0.2 nm to about 40 nm thick.

5. The perpendicular magnetic recording medium as in claim 4, wherein:

said at least one interlayer is from about 4 nm to about 12 nm thick.

6. The perpendicular magnetic recording medium as in claim 1, wherein:

said non-magnetic spacer layer is from about 2 to about 20 Å

thick, selected to maximize anti-ferromagnetic or ferromagnetic coupling between the stabilization layer and the main recording layer, and comprises a material selected from the group consisting of Ru, Rh, Ir, Cr, Cu, Re, V, and their alloys; and

said layer stack (b) optionally further comprises;

at least one ferromagnetic interface layer at at least one interface between said non-magnetic spacer layer and said main recording layer and said stabilization layer.

7. The perpendicular magnetic recording medium as in claim 6, wherein:

said non-magnetic spacer layer further comprises an oxide material containing one or more elements selected from the group consisting of Al, Si, Ti, V, Mn, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf and W.

8. The perpendicular magnetic recording medium as in claim 7, wherein:

said non-magnetic spacer layer comprises Ru with 2 to 10 molar % of SiO₂, or Ru with 2 to 7 molar % of Nb₂O₅, or Ru with 2 to 7 molar % of Cr₂O₃, or Ru with 2 to 9 molar % of WO₃, or Ru with 2 to 15 molar % of ZrO₂, or Ru with 2 to 15 molar % of TiO₂.

9. The perpendicular magnetic recording medium as in claim 6, wherein:

said at least one ferromagnetic interface layer is present at the interface between said non-magnetic spacer layer and said main recording layer.

10. The perpendicular magnetic recording medium as in claim 6, wherein:

said at least one ferromagnetic interface layer is present at the interface between said non-magnetic spacer layer and said stabilization layer.

11. The perpendicular magnetic recording medium as in claim 6, wherein:

said at least one ferromagnetic interface layer is present at the interfaces between said non-magnetic spacer layer and each of said main recording layer and said stabilization layer.

12. The perpendicular magnetic recording medium as in claim 6, wherein:

said at least one ferromagnetic interface layer comprises an about 1 monolayer to an about 40 Å

thick layer of a ferromagnetic material having a saturation magnetization value M_s>

400 emu/cc.

13. The perpendicular magnetic recording medium as in claim 12, wherein:

said at least one ferromagnetic interface layer comprises a layer of a high moment element or alloy selected from Fe or Co, and their alloys containing at least one element selected from Cr, Pt, Ta, B, Mo, Ru, Si, Ge, Nb and Ni.

14. The perpendicular magnetic recording medium as in claim 12, wherein:

said at least one ferromagnetic interface layer comprises Co and one or more elements selected from the group consisting of Cr, Pt, Ta, B, Fe, Cu, Ag, W, Mo, Ru, Si, Ge Nb and Ni, and at least one oxide material containing one or more elements selected from the group consisting of Al, Si, Ti, V, Mn, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf and W.

15. The perpendicular magnetic recording medium as in claim 1, wherein:

said layer stack further includes at least one additional stacked pair of layers between said main recording layer and said non-magnetic spacer layer, comprising a perpendicularly anisotropic magnetic layer and a non-magnetic spacer layer, such that said layer stack comprises alternating magnetic layers and non-magnetic spacer layers, and magnetic energies of said magnetic layers and coupling energies between said magnetic layers are selected to provide anti-parallel alignment of magnetic moments of adjacent magnetic layers during data storage in said medium.

16. The perpendicular magnetic recording medium as in claim 15, further comprising:

at least one ferromagnetic interface layer at at least one interface between said non-magnetic spacer layers and said main recording layers and said stabilization layer.

17. The perpendicular magnetic recording medium as in claim 1, wherein:

said stabilization layer and said main recording layer each comprise at least one layer that is about 3 to about 300 Å

thick and comprises a ferromagnetic Co alloy containing at least one element selected from Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe, Ni, and W and at least one oxide material containing one or more elements selected from the group consisting of Cr, Al, Si, Ti, V, Mn, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf and W.

18. The perpendicular magnetic recording medium as in claim 17, wherein:

said stabilization layer and said main recording layer comprises a CoPt or CoPtCr alloy with up to 12 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 10 molar % of SiO₂ and up to 10 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 7 molar % of Nb₂O₅ and up to 10 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 9 molar % of WO₃ and up to 10 molar % of Cr and Co oxide or a CoPt or CoPtCr alloy with 2 to 15 molar % of ZrO₂ and up to 10 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 15 molar % of TiO₂ and up to 10 molar % of Cr and Co oxide.

19. The perpendicular magnetic recording medium as in claim 18, wherein the up to 10 or 12 molar % of Cr and Co oxide include Cr₂O₃ and CoO, respectively.

20. The perpendicular magnetic recording medium as in claim 1, wherein:

said stabilization layer comprises a layer of a [CoX/(Pd or Pt)]_n, [FeX/(Pd or Pt)]_n, or [FeCoX/(Pd or Pt)]_n multilayer magnetic superlattice structure where n is an integer from about 1 to about 25 and X is at least one element selected from the group consisting of Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Ni, Cr and W.

21. The perpendicular magnetic recording medium as in claim 1, wherein:

said non-magnetic substrate comprises a material selected from the group consisting of;

Al, NiP-plated Al, Al-Mg alloys, other Al-based alloys, other non-magnetic metals, other non-magnetic alloys, glass, ceramics, polymers, glass-ceramics, and composites and/or laminates thereof;

said underlayer comprises an about 500 to about 4,000 Å

thick layer comprised of at least one soft ferromagnetic material selected from Ni, NiFe (Permalloy), Co, CoZr, CoZrCr, CoZrNb, CoTaZr, CoFe, Fe, FeN, FeSiAl, FeSiAlN, FeTaC, FeAlN, FeCo, FeCoNi, CoFeCr, CoFeCrB, FeTaN, CoFeZr, FeCoB, and FeCoC.

22. The perpendicular magnetic recording medium as in claim 1, further comprising:

(c) a protective overcoat layer on said main recording layer; and

(d) a lubricant topcoat layer over said protective overcoat layer.

23. A perpendicular magnetic recording medium, comprising:

a substrate;

a first ferromagnetic layer;

a non-magnetic spacer layer;

a second ferromagnetic layer comprised of a granular hard ferromagnetic material;

wherein said first ferromagnetic layer and said second ferromagnetic layer are magnetically coupled across said non-magnetic spacer layer.

24. The perpendicular magnetic recording medium as in claim 23, further comprising a layer stack formed over said substrate, in overlying sequence from said substrate:

an underlayer comprised of a magnetically soft ferromagnetic material or a plurality of layers of magnetically soft ferromagnetic material separated by thin non-magnetic spacer layers;

at least one interlayer;

said first ferromagnetic layer;

said non-magnetic spacer layer; and

said second ferromagnetic layer, wherein

said first ferromagnetic layer is a stabilization layer and said second ferromagnetic layer is a main recording layer.

25. The perpendicular magnetic recording medium as in claim 24, further comprising:

at least one ferromagnetic interface layer at at least one interface between said non-magnetic spacer layers and said second ferromagnetic layer and said first ferromagnetic layer.

26. The perpendicular magnetic recording medium as in claim 24, wherein:

said second ferromagnetic layer and said first ferromagnetic layer each comprise at least one layer that is about 3 to about 300 Å

thick and comprises a ferromagnetic Co alloy containing at least one element selected from Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe, Ni, and W and at least one oxide material containing one or more elements selected from the group consisting of Cr, Al, Si, Ti, V, Mn, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf and W.

27. The perpendicular magnetic recording medium as in claim 26, wherein:

said first ferromagnetic layer and said second ferromagnetic layer comprises a CoPt or CoPtCr alloy with up to 12 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 10 molar % of SiO₂ and up to 10 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 7 molar % of Nb₂O₅ and up to 10 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 9 molar % of WO₃ and up to 10 molar % of Cr and Co oxide or a CoPt or CoPtCr alloy with 2 to 15 molar % of ZrO₂ and up to 10 molar % of Cr and Co oxide, or a CoPt or CoPtCr alloy with 2 to 15 molar % of TiO₂ and up to 10 molar % of Cr and Co oxide.

28. The perpendicular magnetic recording medium as in claim 27, wherein the up to 10 or 12 molar % of Cr and Co oxide include Cr₂O₃ and CoO, respectively.

29. The perpendicular magnetic recording medium as in claim 24, wherein:

said first ferromagnetic layer comprises a layer of a [CoX/(Pd or Pt)]_n, [FeX/(Pd or Pt)]_n, or [FeCoX/(Pd or Pt)]_n multilayer magnetic superlattice structure where n is an integer from about 1 to about 25 and X is at least one element selected from the group consisting of Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Ni, Cr and W.