Heat-assisted magnetic recording (HAMR) medium with multilayered underlayer for the recording layer
A heat-assisted magnetic recording (HAMR) medium has a multilayered underlayer between the heat-sink layer and the recording layer. One embodiment of the underlayer is a multilayer of a thermal barrier layer consisting essentially of MgO and TiO, and a seed layer containing MgO and nitrogen (N) directly on the thermal barrier layer, with the recording layer on and in contact with the seed layer. The interface between the thermal barrier layer and the seed layer contains Ti and N, some of which may be present as TiN to act as a diffusion barrier to prevent diffusion of the Ti into the recording layer. The Ti-containing thermal barrier layer has a higher thermal resistivity than the conventional MgO thermal barrier/seed layer and thus allows for reduced laser power to the recording layer while still achieving a high thermal gradient at the recording layer.
1. A heat-assisted magnetic recording (HAMR) medium comprising:
a substrate;
a heat-sink layer on the substrate;
a magnetic recording layer comprising a chemically-ordered alloy selected from a FePt alloy and a CoPt alloy; and
a multilayered underlayer between the heat-sink layer and the recording layer and comprising a thermal barrier layer consisting of MgO and TiO, a seed layer consisting of MgO and nitrogen (N), and a diffusion barrier comprising Ti and N between the thermal barrier layer and the seed layer, wherein the recording layer is on and in contact with the seed layer.
2. The medium of claim 1 wherein the thermal barrier layer has a composition of the form MgO (100-x) TiO (x) , where x is greater than or equal to 40 and less than or equal to 90.
3. The medium of claim 1 wherein the thermal barrier layer has a thickness greater than or equal to 2 nm and less than or equal to 6 nm.
4. The medium of claim 1 wherein the diffusion barrier comprises TiN.
5. The medium of claim 1 wherein the seed layer has a thickness greater than or equal to 1 nm and less than or equal to 5 nm.
6. The medium of claim 1 wherein the heat-sink layer comprises a heat-sink layer selected from one or more of Cu, Au, Ag, Cr, Mo, W and their alloys.
7. The medium of claim 6 wherein the heat-sink layer comprises multiple heat-sink layers.
8. The medium of claim 1 wherein the magnetic recording layer comprises a substantially chemically-ordered alloy comprising Pt and an element selected from Fe and Co, and a segregant selected from one or more of C, SiO 2 , TiO 2 , TaO x , ZrO 2 , SiC, SiN, TiC, TiN, B, BC and BN.
9. The medium of claim 1 wherein the magnetic recording layer comprises a multilayered structure wherein each layer comprises a substantially chemically-ordered alloy comprising Pt and an element selected from Fe and Co, and a segregant selected from one or more of C, SiO 2 , TiO 2 , TaO x , ZrO 2 , SiC, SiN, TiC, TiN, B, BC and BN.
10. The medium of claim 1 wherein the magnetic recording layer comprises a substantially chemically-ordered pseudo-binary FePtX alloy in the L1 0 phase, where X is one or more of Ni, Au, Cu, Pd, Mn and Ag.
11. 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 layer of said medium and supporting a near-field transducer.