Magnetic recording medium and magnetic recording device

• US 20060222901A1
• Filed: 03/14/2006
• Published: 10/05/2006
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Showa Denko KK
• Original Assignee: Fujitsu Limited
• Inventors: Inamura, Ryosaku, Kaitsu, Isatake, Uzumaki, Takuya
• Granted Patent: US 7,611,783 B2
• Time in Patent Office: Days
• US Class Current: 428/827
• CPC Class Codes: G11B 5/65 characterised by its composition G11B5/66 takes 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 5/667 including a soft magnetic layer
• 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 5/7369 Two or more non-magnetic underlayers, e.g. seed layers or barrier layers
• CPC Class Codes: G11B 5/737 Physical structure of underlayer, e.g. texture
• 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

Abstract

A magnetic recording medium includes; a base member; an underlayer formed on the base member; a main recording layer formed on the underlayer, and a writing assist layer formed on or under the main recording layer in contact with the main recording layer. The main recording layer has perpendicular magnetic anisotropy with an anisotropic magnetic field of H_k1 and an inclination of a reversal part of a magnetization curve of a₁. The writing assist layer has an anisotropic magnetic field of H_k2 and an inclination of a reversal part of a magnetization curve of a₂. The anisotropic magnetic fields H_k1 and H_k2 and the inclinations a₁ and a₂ satisfy H_k1>H_k2 and a₂>a₁.

Claims

1. A magnetic recording medium, comprising:

a base member;

an underlayer formed on the base member;

a main recording layer formed on the underlayer, the main recording layer having perpendicular magnetic anisotropy with an anisotropic magnetic field of H_k1 and an inclination of a reversal part of a magnetization curve of a₁; and

a writing assist layer formed on or under the main recording layer in contact with the main recording layer, the writing assist layer having an anisotropic magnetic field of H_k2 and an inclination of a reversal part of a magnetization curve of a₂,

wherein the anisotropic magnetic fields H_k1 and H_k2 and the inclinations a₁ and a₂ satisfy H_k1>

H_k2 and a₂>

a₁.

2. The magnetic recording medium according to claim 1, wherein the main recording layer has a granular structure composed of a non-magnetic material and magnetic grains dispersed in the non-magnetic material.

3. The magnetic recording medium according to claim 1, wherein a saturated magnetization (Ms) of the writing assist layer falls within a range of equal to or grater than 350 emu/cc and equal to or less than 850 emu/cc.

4. The magnetic recording medium according to claim 2, wherein the writing assist layer and the magnetic grains are composed of an alloy containing cobalt, chromium, and platinum.

5. The magnetic recording medium according to claim 4, wherein a content of chromium in the magnetic grains is lower than that of the writing assist layer and a content of platinum is higher than that of the writing assist layer.

6. The magnetic recording medium according to claim 2, wherein the magnetic grains are composed of an alloy containing cobalt and iron.

7. The magnetic recording medium according to claim 6, wherein the magnetic grains are added with copper or silver.

8. The magnetic recording medium according to claim 2, wherein the non-magnetic material is an oxide or a nitride of one selected from the group consisting of silicon, titanium, chromium, and zirconium.

9. The magnetic recording medium according to claim 1, wherein the writing assist layer is composed of an alloy layer containing cobalt and chromium.

10. The magnetic recording medium according to claim 9, wherein the alloy layer containing cobalt and chromium is added with one selected from the group consisting of platinum, tantalum, boron, copper, and nickel.

11. The magnetic recording medium according to claim 1, wherein the underlayer is a laminate film including a backing layer having a soft magnetic layer and a non-magnetic layer formed in a uppermost layer.

12. The magnetic recording medium according to claim 11, wherein the soft magnetic layer is composed of a soft magnetic amorphous material.

13. The magnetic recording medium according to claim 12, wherein the soft magnetic amorphous material is one selected from the group consisting of a cobalt-zirconium alloy and an iron-carbon alloy.

14. The magnetic recording medium according to claim 11, wherein the main recording layer is formed on the non-magnetic layer in contact with the non-magnetic layer and has a granular structure including a non-magnetic material and magnetic grains dispersed in the non-magnetic material, and

the non-magnetic layer has a same crystal structure as that of the magnetic grains.

15. The magnetic recording medium according to claim 14, wherein the crystal structure is an hcp structure.

16. The magnetic recording medium according to claim 15, wherein the underlayer includes an orientation control layer having a fcc crystal structure, and the non-magnetic layer is formed on the orientation control layer.

17. The magnetic recording medium according to claim 16, wherein the orientation control layer is composed of one selected from the group consisting of platinum, palladium, a nickel-iron alloy, a nickel-iron-silicon alloy, aluminum, copper, and indium.

18. A magnetic recording device, comprising:

a magnetic recording medium which includes;

a base member;

an underlayer formed on the base member;

a main recording layer formed on the underlayer, the main recording layer having perpendicular magnetic anisotropy with an anisotropic magnetic field of H_k1 and an inclination of a reversal part of a magnetization curve of a₁; and

a writing assist layer formed on or under the main recording layer in contact with the main recording layer, the writing assist layer having an anisotropic magnetic field of H_k2 and an inclination of a reversal part of a magnetization curve of a₂; and

a magnetic head opposing to the magnetic recording medium, wherein

the anisotropic magnetic fields H_k1 and H_k2 and the inclinations a₁ and a₂ satisfy H_k1>

H_k2 and a₂>

a₁.

19. The magnetic recording device according to claim 18, wherein the main recording layer has a granular structure composed of a non-magnetic material and magnetic grains dispersed in the non-magnetic material.

20. The magnetic recording medium according to claim 18, wherein the writing assist layer and the magnetic grains are composed of an alloy containing cobalt, chromium, and platinum.