MAGNETIC SIGNAL REPRODUCTION SYSTEM AND MAGNETIC SIGNAL REPRODUCTION METHOD

• US 20080297950A1
• Filed: 05/29/2008
• Published: 12/04/2008
• Est. Priority Date: 05/31/2007
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: NOGUCHI, Hitoshi, ENDO, Yasushi, SHIMIZU, Osamu
• Granted Patent: US 8,164,857 B2
• Time in Patent Office: Days
• US Class Current: 360/313
• CPC Class Codes: G11B 5/00821 using stationary heads
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/71 characterised by the lubricant
• CPC Class Codes: G11B 5/714 characterised by the dimension of the magnetic particles

Abstract

The magnetic signal reproduction system comprises a magnetic recording medium comprising a magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support; and a reproduction head, wherein a number of protrusions equal to or greater than 10 nm in height on the magnetic layer surface, as measured by an atomic force microscope, ranges from 50 to 2500/10,000 μm², a quantity of lubricant on the magnetic layer surface, denoted as a surface lubricant index, ranges from 0.5 to 5.0, a surface abrasive occupancy of the magnetic layer ranges from 2 to 20 percent, and the reproduction head is a magnetoresistive magnetic head comprising a spin-valve layer.

Claims

1. A magnetic signal reproduction system comprising:

a magnetic recording medium comprising a magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support; and

a reproduction head,

wherein

a number of protrusions equal to or greater than 10 nm in height on the magnetic layer surface, as measured by an atomic force microscope, ranges from 50 to 2500/10,000 μ

m²,

a quantity of lubricant on the magnetic layer surface, denoted as a surface lubricant index, ranges from 0.5 to 5.0,

a surface abrasive occupancy of the magnetic layer ranges from 2 to 20 percent, and the reproduction head is a magnetoresistive magnetic head comprising a spin-valve layer.

2. The magnetic signal reproduction system according to claim 1, wherein the ferromagnetic powder is a hexagonal ferrite powder.

3. The magnetic signal reproduction system according to claim 2, wherein the hexagonal ferrite powder has a mean plate diameter ranging from 10 to 50 nm.

4. The magnetic signal reproduction system according to claim 1, wherein the magnetic layer has a thickness ranging from 10 to 150 nm.

5. The magnetic signal reproduction system according to claim 1, wherein the reproduction head comprises at least a first shield layer, a first gap layer, a spin-valve layer, a second gap layer and a second shield layer in this order on a support.

6. The magnetic signal reproduction system according to claim 1, wherein the reproduction head comes in sliding contact with the magnetic recording medium during signal reproduction.

7. The magnetic signal reproduction system according to claim 6, wherein at least a surface that contacts with the magnetic recording medium during signal reproduction of the first shield layer and/or the second shield layer is comprised of amorphous alloy comprising cobalt as a main component.

8. The magnetic signal reproduction system according to claim 6, wherein the reproduction head has an electrode layer applying an electric current to the spin-valve layer, and at least a surface that contacts with the magnetic recording medium during signal reproduction of the electrode layer is comprised of metal comprising tantalum as a main component.

9. The magnetic signal reproduction system according to claim 1, wherein the spin-valve layer exhibits a giant magnetoresistive effect.

10. A magnetic signal reproduction method reproducing signals, that have been recorded on a magnetic recording medium, with a reproduction head, wherein

the magnetic recording medium comprises a magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support,

a number of protrusions equal to or greater than 10 nm in height on the magnetic layer surface, as measured by an atomic force microscope, ranges from 50 to 2500/10,000 μ

m²,

a quantity of lubricant on the magnetic layer surface, denoted as a surface lubricant index, ranges from 0.5 to 5.0,

a surface abrasive occupancy of the magnetic layer ranges from 2 to 20 percent, and

the reproduction head is a magnetoresistive magnetic head comprising a spin-valve layer.

11. The magnetic signal reproduction method according to claim 10, wherein the ferromagnetic powder is a hexagonal ferrite powder.

12. The magnetic signal reproduction method according to claim 11, wherein the hexagonal ferrite powder has a mean plate diameter ranging from 10 to 50 nm.

13. The magnetic signal reproduction method according to claim 10, wherein the magnetic layer has a thickness ranging from 10 to 150 nm.

14. The magnetic signal reproduction method according to claim 10, wherein the reproduction head comprises at least a first shield layer, a first gap layer, a spin-valve layer, a second gap layer and a second shield layer in this order on a support.

15. The magnetic signal reproduction method according to claim 10, wherein the reproduction head comes in sliding contact with the magnetic recording medium during signal reproduction.

16. The magnetic signal reproduction method according to claim 15, wherein at least a surface that contacts with the magnetic recording medium during signal reproduction of the first shield layer and/or the second shield layer is comprised of amorphous alloy comprising cobalt as a main component.

17. The magnetic signal reproduction method according to claim 15, wherein the reproduction head has an electrode layer applying an electric current to the spin-valve layer, and at least a surface that contacts with the magnetic recording medium during signal reproduction of the electrode layer is comprised of metal comprising tantalum as a main component.

18. The magnetic signal reproduction method according to claim 10, wherein the spin-valve layer exhibits a giant magnetoresistive effect.