Stabilized recording media including coupled discontinuous and continuous magnetic layers

• US 6,777,112 B1
• Filed: 10/09/2001
• Issued: 08/17/2004
• Est. Priority Date: 10/10/2000
• Status: Expired due to Term

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Harkness, Samuel D., Girt, Erol, Richter, Hans Jürgen
• Primary Examiner(s): Rickman, Holly
• Application Number:
  US09/971,693
• Time in Patent Office: 1,043 Days
• Field of Search: 428/694.TM, 428/694.TS, 428/336, 428/212, 428/900
• US Class Current: 428/828
• CPC Class Codes: G11B 5/66 the record carriers consisting of several layers
• CPC Class Codes: G11B 5/674 having differing macroscopic or microscopic structures, e.g. differing crystalline lattices, varying atomic structures or differing roughnesses
• 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: G11B 5/7369 Two or more non-magnetic underlayers, e.g. seed layers or barrier layers
• CPC Class Codes: G11B 5/7379 Seed layer, e.g. at least one non-magnetic layer is specifically adapted as a seed or seeding layer
• CPC Class Codes: G11B 5/73913 Composites or coated substrates
• CPC Class Codes: G11B 5/73917 Metallic substrates, i.e. elemental metal or metal alloy substrates
• CPC Class Codes: G11B 5/73919 Aluminium or titanium elemental or alloy substrates
• CPC Class Codes: G11B 5/73921 Glass or ceramic substrates
• CPC Class Codes: G11B 5/73923 Organic polymer substrates
• CPC Class Codes: G11B 5/855 Coating only part of a support with a magnetic layer
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A magnetic recording medium having increased thermal stability and signal-to-medium noise ratio (SMNR), comprising a layer stack including, in sequence:

(a) a continuous ferromagnetic layer;

(b) a non-magnetic spacer layer; and

(c) a discontinuous ferromagnetic layer;

wherein the continuous ferromagnetic layer (a) and the discontinuous ferromagnetic layer (c) are ferromagnetically or anti-ferromagnetically coupled together across the non-magnetic spacer layer.

Claims

1. A magnetic recorder medium comprising a layer stack including, in sequence:

(a) a continuous ferromagnetic layer;

(b) a non-magnetic spacer layer; and

(c) a discontinuous ferromagnetic layer;

wherein;

said continuous ferromagnetic layer (a) and said discontinuous ferromagnetic layer (c) are coupled together across said non-magnetic spacer layer; and

said discontinuous ferromagnetic layer (c) is from about 10 to about 300 Å

thick, has a large magnetocrystalline anisotropy greater than about 10⁶ erg/cm³ for obtaining sufficient coercivity at lower saturation magnetization thereof, and includes exchange de-coupled or partially coupled magnetic grains.

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

said continuous ferromagnetic layer (a) comprises a material having less than about 5 at. % of non-magnetic phases for ensuring strong magnetic coupling between adjacent grains, a very high magnetocrystalline anisotropy greater than about 10⁷ erg/cm³ for reducing the width of the magnetic domain walls thereof to less than or equal to the average size of the grains of said discontinuous ferromagnetic layer when the magnetic domains of the continuous ferromagnetic layer are larger than the average grain size in said discontinuous layer, or a high magnetocrystalline anisotropy greater than about 10⁶ erg/cm³ when comprised of coupled single domain grains, and a lower coercivity than that of said discontinuous ferromagnetic layer (c).

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

said continuous ferromagnetic layer (a) is from about 10 to about 200 Å

thick and comprises an alloy material selected from the group consisting of Co₃Pt, MnA1, Nd₂Fe₁₄B, SmCo₅, Sm2Co₁₇, Sm₂Fe₁₇(N,C), Co_100-x-y-zCr_xPt_yB_z, Co_100-x-y-z-wCr_xPt_yNb_zTa_w, and (Pt, Pd)Co., Fe)L1₀ phase.

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

said non-magnetic spacer layer (b) is from about 2 to about 30 Å

thick.

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

said non-magnetic spacer layer (b) provides magnetic or anti-ferromagnetic coupling between said continuous ferromagnetic layer (a) and said discontinuous ferromagnetic layer, depending upon the thickness thereof, and comprises a material selected from the group of Ru, Rh, Ir, Cr, Cu, and their alloys.

6. The magnetic recording medium as in claim 1, formed as a longitudinal recording medium.

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

said discontinuous ferromagnetic layer (c) comprises an alloy material selected from the group consisting of CoCr;

CoCr with one or more added elements selected from Pt, Ta, B, Mo, Ru, Si, Ge, and Nb;

Fe; and

Ni.

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

(d) a substrate having at least one surface for supporting a said layer stack; and

(e) non-magnetic seed and underlayers intermediate said at least one surface of said substrate (d) and said layer stack for controlling the crystallographic texture of at least one of said ferromagnetic layers of said layer stack.

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

said substrate (d) comprises a non-magnetic material selected from the group consisting of Al, Al-based alloys, NiP-plated Al, other non-magnetic metals, other non-magnetic metal alloys, glass, ceramics, glass-ceramics, polymers, and laminates and composites thereof; and

said non-magnetic seed and underlayers (e) comprises materials selected from the group consisting of Ni—

Al, Ni—

Al—

Ru, Ni—

Al—

Ti, Fe—

Al, Ru—

Al, CoTi, Ta, Ta—

N, Cr, Cr—

Ta, Cr—

W, Cr—

Mo, Cr—

V, Cr—

Ti, Cr—

Ru, and Cr—

Ru—

Ta.

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

said discontinuous ferromagnetic layer (c) of said layer stack is proximate said at least one surface of said substrate (d).

11. The magnetic recording medium as in claim 10 further comprising a stacked layer pair intermediate said discontinuous ferromagnetic layer (c) of said layer stack and said non-magnetic seed and underlayers (e), said stacked layer pair consisting of a continuous ferromagnetic layer (a) or a discontinuous ferromagnetic layer (c) adjacent said non-magnetic seed and underlayers (e) and a non-magnetic spacer layer (b) adjacent said discontinuous ferromagnetic layer (c) of said layer stack.

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

said continuous ferromagnetic layer (a) of said layer stack is proximate said at least one surface of said substrate (d).

13. The magnetic recording medium as in claim 12, further comprising a stacked layer pair intermediate said continuous ferromagnetic layer (a) of said layer stack and said non-magnetic seed and underlayers (e), said stacked layer pair consisting of a continuous ferromagnetic layer (a) or a discontinuous ferromagnetic layer

(c) adjacent said non-magnetic seed and underlayers (e) and a non-magnetic spacer layer

(b) adjacent said continuous ferromagnetic layer (a) of said layer stack.

14. The magnetic recording medium as in claim 8, further comprising:

(f) a protective overcoat layer over said stack; and

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

15. A magnetic recording medium, comprising:

(a) a layer stack including, in sequence;

(i) a continuous ferromagnetic layer;

(ii) a non-magnetic spacer layer; and

(iii) a discontinuous ferromagnetic layer;

wherein said continuous ferromagnetic layer (i) and the discontinuous ferromagnetic layer each comprises a material having a very high magnetocrystalline anisotropy greater than about 10⁶ erg/cm³ for obtaining sufficient coercivity at lower saturation magnetization thereof and minimizing the width of the magnetic domain walls, respectively, the continuous ferromagnetic layer has a lower coercivity than that of said discontinuous ferromagnetic layer (iii), said non-magnetic spacer layer provides magnetic or anti-ferromagnetic coupling between said continuous ferromagnetic layer (i) and said discontinuous ferromagnetic layer (iii), depending upon its thickness; and

said discontinuous ferromagnetic layer is from about 10 to about 300 Å

thick, has a large magnetocrystalline anisotropy greater than about 10⁶ erg/cm³ for obtaining sufficient coercivity at lower saturation magnetization thereof, and includes exchange de-coupled or partially magnetic grains.

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

either said continuous ferromagnetic layer (i) or said discontinuous ferromagnetic layer (iii) of said layer stack (a) is proximate said at least one surface of said substrate (b).

17. The magnetic recording medium as in claim 16, further comprising a stacked layer pair intermediate said layer stack (a) and said non-magnetic seed and underlayers (c), said stacked layer pair consisting of a continuous ferromagnetic layer (i) or a discontinuous ferromagnetic layer (iii) adjacent said non-magnetic seed and underlayer (c) and a non-magnetic spacer layer (ii) adjacent said layer stack (a).

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

(d) a protective overcoat layer over said layer stack (a); and

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