Heat-assisted magnetic recording (HAMR) medium with heat-sink layer having anisotropic thermal conductivity

Patent metadata

Field	Value
Publication number	US-10109309-B1
Application number	US-201715694276-A
Country	US
Kind code	B1
Filing date	Sep 1, 2017
Priority date	Sep 1, 2017
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

A heat-assisted magnetic recording (HAMR) medium includes a perpendicular magnetic recording layer (typically a chemically-ordered FePt alloy), a seed/thermal barrier layer (typically MgO) below the recording layer, and a heat-sink layer with anisotropic thermal conductivity below the seed/thermal barrier layer. The in-plane thermal conductivity of the heat-sink layer is greater than its out-of-plane thermal conductivity. The heat-sink layer may be selected from hexagonal boron nitride (h-BN), hexagonal graphite, and the 6H polytype of hexagonal silicon carbide (6H-SiC). If the heat-sink layer is h-BN, the h-BN layer is formed on a seed layer and has its c-axis oriented out-of-plane (substantially orthogonal to the surface of the medium substrate).

First claim

What is claimed is:

1. A heat-assisted magnetic recording medium comprising:
a substrate;
a heat-sink layer on the substrate, the heat-sink layer selected from the group consisting of hexagonal boron nitride (h-BN), hexagonal graphite, and the 6H polytype of hexagonal silicon carbide (6H-SiC) and having anisotropic thermal conductivity, the thermal conductivity in the plane of the heat-sink layer being greater than the thermal conductivity normal to the plane of the heat-sink layer;
a magnetic recording layer; and
a seed/thermal barrier layer for the recording layer on the heat-sink layer, wherein the recording layer is on and in contact with the seed/thermal barrier layer.

2. The medium of claim 1 wherein the ratio of thermal conductivity in the plane of the heat-sink layer to the thermal conductivity normal to the plane of the heat-sink layer is greater than 1.2.

3. The medium of claim 2 wherein the thermal conductivity in the plane of the heat-sink layer is greater than 50 W/mK.

4. The medium of claim 1 wherein the heat-sink layer comprises hexagonal boron nitride (h-BN) having its c-axis oriented substantially normal to the plane of the heat-sink layer, and further comprising a seed layer between the substrate and the heat-sink layer, wherein the heat-sink layer is on and in contact with the seed layer.

5. The medium of claim 4 wherein the seed layer for the heat-sink layer comprises a material having hexagonal crystalline structure with its [002] crystallographic direction oriented out-of-plane.

6. The medium of claim 5 wherein the seed layer for the heat-sink layer comprises a material selected from the group consisting of Ru, Ti, Co, Re, Zr and Zn.

7. The medium of claim 5 further comprising an amorphous adhesion layer between the substrate and the seed layer for the heat-sink layer, wherein the seed layer for the heat-sink layer is on and in contact with the adhesion layer.

8. The medium of claim 7 wherein the adhesion layer comprises an alloy comprising two or more elements selected from the group consisting of Cr, Ta and Ti.

9. The medium of claim 4 wherein the seed layer for the heat-sink layer comprises a material having a face-centered-cubic crystalline structure with its [111] crystallographic direction oriented out-of-plane.

10. The medium of claim 9 wherein the seed layer for the heat-sink layer comprises a material selected from the group consisting of Au, Ag, Sr, Ni, Pt, Pd, Cu, Ir and Rh.

11. The medium of claim 1 further comprising an amorphous underlayer between the heat-sink layer and the seed/thermal barrier layer, wherein the seed/thermal barrier layer is on and in contact with the underlayer.

12. The medium of claim 1 wherein the magnetic recording layer comprises a chemically-ordered alloy selected from a FePt alloy and a CoPt alloy, and wherein the seed/thermal barrier layer for the recording layer comprises MgO.

13. A heat assisted magnetic recording (HAMR) disk drive comprising:
the medium according to claim 1 wherein said medium is a rotatable HAMR disk; and
a carrier maintained near the magnetic recording layer of said medium and supporting a HAMR head, the HAMR head comprising a near-field transducer.

14. A heat-assisted magnetic recording (HAMR) disk comprising:
a disk substrate having a substantially planar surface;
a heat-sink layer on the substrate, the heat-sink layer comprising hexagonal boron-nitride (h-BN) having its c-axis oriented substantially orthogonal to the substrate surface;
a seed layer for the heat-sink layer between the substrate and the heat-sink layer, wherein the heat-sink layer is on and in contact with the seed layer;
a seed/thermal barrier layer comprising MgO on the heat-sink layer; and
a perpendicular magnetic recording layer comprising a chemically-ordered alloy selected from a FePt alloy and a CoPt alloy on and in contact with the seed/thermal barrier layer.

15. The disk of claim 14 wherein the heat-sink layer comprising h-BN has anisotropic thermal conductivity, the ratio of thermal conductivity substantially orthogonal to the c-axis to thermal conductivity substantially parallel to the c-axis being greater than 1.2.

16. The disk of claim 15 wherein the thermal conductivity in the plane of the heat-sink layer is greater than 50 W/mK.

17. The disk of claim 14 wherein the seed layer for the heat-sink layer comprises a material having hexagonal crystalline structure with its [002] crystallographic direction oriented out-of-plane.

18. The disk of claim 14 wherein the seed layer for the heat-sink layer comprises a material having a face-centered-cubic crystalline structure with its [111] crystallographic direction oriented out-of-plane.

19. The disk of claim 14 further comprising an amorphous adhesion layer on and in contact with the substrate surface, wherein the seed layer for the heat-sink layer is on and in contact with the adhesion layer.

20. The disk of claim 14 further comprising an amorphous underlayer between the heat-sink layer and the seed/thermal barrier layer, wherein the seed/thermal barrier layer is on and in contact with the underlayer.

21. A heat assisted magnetic recording (HAMR) disk drive comprising:
the disk according to claim 14 ; and
a gas-bearing slider maintained near the magnetic recording layer of said disk and supporting a HAMR head, the HAMR head comprising a near-field transducer.

22. A heat-assisted magnetic recording medium comprising:
a substrate;
a heat-sink layer on the substrate, the heat-sink layer having anisotropic thermal conductivity, the thermal conductivity in the plane of the heat-sink layer being greater than the thermal conductivity normal to the plane of the heat-sink layer;
a magnetic recording layer;
a seed/thermal barrier layer for the recording layer on the heat-sink layer, wherein the recording layer is on and in contact with the seed/thermal barrier layer; and
an amorphous underlayer between the heat-sink layer and the seed/thermal barrier layer, wherein the seed/thermal barrier layer is on and in contact with the underlayer.

Assignees

• Western Digital Tech Inc

Inventors

• Jubert Pierre-Olivier
• Srinivasan Kumar

Classifications

• G11B5/732

  Physics · mapped topic

• G11B13/08

  using near-field interactions or transducing means and at least one other method or means for recording or reproducing · CPC title

• G11B5/49

  Fixed mounting {or arrangements, e.g. one head per track} · CPC title

• G11B2005/0021

  Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal · CPC title

• H01F10/10

  characterised by the composition · CPC title