Erasure-resistant perpendicular magnetic recording media, systems & method of manufacturing same

• US 20060146445A1
• Filed: 01/04/2005
• Published: 07/06/2006
• Est. Priority Date: 01/04/2005
• Status: Abandoned Application

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Chen, Jianping, Harkness, Samuel Dacke IV, Nolan, Thomas Patrick, Chang, Chunghee
• Application Number:
  US11/028,224
• Publication Number:
  US 20060146445A1
• Time in Patent Office: Days
• US Class Current: 360/135
• CPC Class Codes: G11B 2005/0029 using magnetisation components of the recording layer disposed mainly perpendicularly to the record carrier surface
• CPC Class Codes: G11B 5/1278 specially adapted for magnetisations perpendicular to the surface of the record carrier
• CPC Class Codes: G11B 5/667 including a soft magnetic layer
• CPC Class Codes: G11B 5/82 Disk carriers

Abstract

A perpendicular magnetic recording medium adapted for use with a single-pole magnetic transducer head comprises a non-magnetic substrate having a surface, and a layer stack formed over the substrate surface, comprising, in overlying sequence from the substrate surface:

• • (i) a magnetically soft underlayer (SUL) having a magnetic saturation value M_s and a thickness t; (ii) at least one non-magnetic interlayer; and (iii) at least one magnetically hard perpendicular recording layer;
  • wherein the product M_st of the SUL is selected to have a minimum value which provides a desired amount of head field channeling but is sufficiently large to provide a desired reduction of erasure of written bits.

Claims

1. A 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;

(i) a magnetically soft underlayer (SUL) having a magnetic saturation value M_s(SUL) and a thickness t;

(ii) at least one non-magnetic interlayer; and

(iii) at least one magnetically hard perpendicular recording layer;

wherein the product (M_s(SUL)t) of said magnetic saturation (M_s(SUL)) and said thickness (t) of said SUL has a minimum value which provides a desired amount of transducer head field channeling but is sufficiently large to provide a desired reduction of erasure of written bits.

2. The recording medium as in claim 1, adapted for use in a magnetic recording system including a single pole magnetic transducer head comprising a main pole having a length λ

, a magnetic saturation value M_s(head), a saturation current I_sat, and a write current I_w;

wherein said thickness t of said SUL is determined based upon the design rule;

t>

(λ

M_s(head)I_w)/M_s(SUL)I_sat

in order to eliminate written bit erasure due to a head field traversing laterally away from a written track and saturating a head pole comer.

3. The recording medium as in claim 2, wherein said write current I_w is equal to said saturation current I_sat, whereby said thickness t of said SUL is determined based upon the design rule:

t>

(λ

M_s(head)/M_s(SUL).

4. The recording medium as in claim 2, wherein said thickness t of said SUL is selected from the following:

(a) the calculated thickness t_calc according to said design rule;

(b) between about 0.7 and about 1.5 times t_calc; and

(c) between about 0.8 and about 1.2 times t_calc

5. The recording medium as in claim 1, wherein:

said SUL comprises a layer of an amorphous magnetic material and includes a smooth surface facing said magnetically hard recording layer.

6. The recording medium as in claim 5, wherein:

said amorphous magnetic material of said SUL is free from low frequency grain noise and stripe domains and has a high M_s(SUL) value at least about 1,500 emu/cm³ for minimizing said thickness t of said SUL providing said M_s(SUL)t product.

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

M_s(SUL)t of said SUL is <

˜

15 memu/cm².

8. The recording medium as in claim 6, wherein:

M_s(SUL)t of said SUL is >

˜

15 memu/cm².

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

said SUL is a laminated structure comprising a plurality of layers of said amorphous magnetic material separated by respective thin spacer layers of a non-magnetic material or a pseudo-laminated structure comprising a stacked plurality of contacting sub-layers of said amorphous magnetic material.

10. The recording medium as in claim 1, wherein:

said non-magnetic substrate comprises glass or an Al-based alloy with an adhesion layer comprising a non-magnetic amorphous material on said surface, and said layer stack includes a laminated SUL comprised of a plurality of amorphous Fe-based alloy layers separated by amorphous, non-magnetic spacer layers, an hcp interlayer with <

0001>

preferred growth orientation, a small-grain, low exchange coupled, hcp Co-based alloy magnetic recording layer, a hard carbon-containing protective overcoat, and a lubricant topcoat.

11. A perpendicular magnetic recording system, comprising:

(a) a single-pole magnetic transducer head comprising a main pole having a length λ

, a magnetic saturation value M_s(head), a saturation current I_sat, and a write current I_w; and

(b) a perpendicular magnetic recording medium adapted for use with said single-pole magnetic transducer head, comprising;

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

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

(1) a magnetically soft underlayer (SUL) having a magnetic saturation value M_s(SUL) and a thickness t;

(2) at least one non-magnetic interlayer; and

(3) at least one magnetically hard perpendicular recording layer;

wherein the product (M_s(SUL)t) of said magnetic saturation (M_(SUL)) and said thickness (t) of said SUL has a minimum value which provides a desired amount of head field channeling but is sufficiently large to provide a desired reduction of erasure of written bits.

12. The perpendicular magnetic recording system as in claim 11, wherein said thickness t of said SUL is determined based upon the design rule:

t>

(λ

M_s(head)I_w)/M_s(SUL)I_sat

in order to eliminate written bit erasure due to a head field traversing laterally away from a written track and saturating a head pole corner.

13. The perpendicular magnetic recording system as in claim 12, wherein said write current I_w is equal to said saturation current I_sat, whereby said thickness t of said SUL is determined based upon the design rule:

t>

(λ

M_s(head)/M_s(SUL).

14. The perpendicular magnetic recording system as in claim 12, wherein said thickness t of said SUL is selected from the following:

(a) the calculated thickness t_calc according to said design rule;

(b) between about 0.7 and about 1.5 times t_calc; and

(c) between about 0.8 and about 1.2 times t_calc

15. The perpendicular magnetic recording system as in claim 11, wherein:

said SUL comprises a layer of an amorphous magnetic material and includes a smooth surface facing said magnetically hard recording layer.

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

said amorphous magnetic material of said SUL is free from low frequency grain noise and stripe domains and has a high M_s(SUL) value at least about 1,500 emu/cm³ for minimizing said thickness t of said SUL providing said M_s(SUL)t product.

17. The perpendicular magnetic recording system as in claim 16, wherein:

M_s(SUL)t of said SUL is <

˜

15 memu/cm².

18. The perpendicular magnetic recording system as in claim 16, wherein:

M_s(SUL)t of said SUL is >

˜

15 memu/cm².

19. The perpendicular magnetic recording system as in claim 18, wherein:

said SUL comprises a laminated structure, wherein said laminated structure comprises a plurality of layers of said amorphous magnetic material separated by respective thin spacer layers of a non-magnetic material or a pseudo-laminated structure comprising a stacked plurality of contacting sub-layers of said amorphous magnetic material.

20. The perpendicular magnetic recording system as in claim 11, wherein:

said non-magnetic substrate comprises glass or an Al-based alloy with an adhesion layer comprising a non-magnetic amorphous material on said surface, and said layer stack includes a laminated SUL comprised of a plurality of amorphous Fe-based alloy layers separated by amorphous, non-magnetic spacer layers, an hcp interlayer with <

0001>

preferred growth orientation, a small-grain, low exchange coupled, hcp Co-based alloy magnetic recording layer, a hard carbon-containing protective overcoat, and a lubricant topcoat.

21. A method of manufacturing a perpendicular magnetic recording medium, comprising:

forming a perpendicular magnetic recording medium, comprising;

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

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

(1) a magnetically soft underlayer (SUL) having a magnetic saturation value M_s(SUL) and a thickness t;

(2) at least one non-magnetic interlayer; and

(3) at least one magnetically hard perpendicular recording layer;

wherein the product (M_s(SUL)t) of said magnetic saturation (M_s(SUL)) and said thickness (t) of said SUL has a minimum value which provides a desired amount of head field channeling but is sufficiently large to provide a desired reduction of erasure of written bits.

22. The method according to claim 21, comprising:

forming a perpendicular magnetic recording medium adapted for use with a single-pole magnetic transducer head comprising a main pole having a length λ

, a magnetic saturation value M_s(head), a saturation current I_sat, and a write current I_w, wherein said thickness t of said SUL is determined based upon the design rule;

t>

(λ

M_s(head)I_w/M_s(SUL)I_sat

in order to eliminate written bit erasure due to a head field traversing laterally away from a written track and saturating a head pole corner.

23. The method according to claim 22, comprising:

forming a perpendicular magnetic recording medium wherein said write current I_w is equal to said saturation current I_sat, and said thickness t of said SUL is determined based upon the design rule;

t>

(λ

M_s(head)/M_s(SUL).

24. The method according to claim 22, comprising:

forming said perpendicular magnetic recording medium wherein said thickness t of said SUL is selected from the following;

(a) the calculated thickness tcalc according to said design rule;

(b) between about 0.7 and about 1.5 times t_calc; and

(c) between about 0.8 and about 1.2 times t_calc

25. The method according to claim 21, comprising

forming a said perpendicular magnetic recording medium wherein said SUL comprises a layer of an amorphous magnetic material which includes a smooth surface facing said magnetically hard recording layer;

and said amorphous magnetic material is free from low frequency noise and stripe domains and has a high M_s(SUL) value at least about 1,500 emu/cm³ for minimizing said thickness t of said SUL.

26. The method according to claim 25, comprising:

forming a perpendicular magnetic recording medium wherein M_s(SUL)t of said SUL is <

˜

15 memu/cm².

27. The method according to claim 25, comprising:

forming a perpendicular magnetic recording medium wherein M_s(SUL)t of said SUL is >

˜

15 memu/cm².

28. The method according to claim 27, comprising:

forming a perpendicular magnetic recording medium wherein said SUL comprises a laminated structure including a plurality of layers of said amorphous magnetic material separated by respective thin spacer layers of a non-magnetic material or a pseudo-laminated structure including a stacked plurality of contacting sub-layers of said amorphous magnetic material.

29. The method according to claim 21, comprising:

forming at least said SUL by sputter deposition.

30. The method according to claim 21, comprising:

providing a non-magnetic glass or Al-based alloy substrate with an adhesion layer comprising a non-magnetic amorphous material on said surface, and forming thereon a layer stack including a laminated SUL comprised of a plurality of amorphous Fe-based alloy layers separated by amorphous, non-magnetic spacer layers, an hcp interlayer with <

0001>

preferred growth orientation, a small-grain, low exchange coupled, hcp Co-based alloy magnetic recording layer, a hard carbon-containing protective overcoat, and a lubricant topcoat.