Thermally-assisted recording (TAR) disk with low thermal-conductivity underlayer
View Patent ↗A thermally-assisted recording (TAR) disk has an improved insulating layer beneath the chemically-ordered FePt (or CoPt) alloy recording layer. The insulating layer is a solid substitution crystalline alloy MgXO, where the element X is selected from nickel (Ni) and cobalt (Co). The composition of the MgXO crystalline solid substitutional alloy is of the form (Mg (100-y) X y )O where y is between 10 and 90, and more preferably between 20 and 80. An optional layer of crystalline “pure” MgO may be located between the MgXO layer and the FePt recording layer and in contact with the recording layer, or between an underlayer and the MgXO layer.
1. A thermally-assisted recording (TAR) disk comprising:
a substrate;
an underlayer on the substrate;
a layer of a crystalline solid substitutional alloy of MgXO on the underlayer, where X is selected from Ni and Co; and
a magnetic recording layer comprising a chemically-ordered alloy selected from FePt, and CoPt on the MgXO layer.
2. The disk of claim 1 wherein the MgXO has a composition of the form (Mg (100-y) X y )O, where y is between 10 and 90.
3. The disk of claim 2 wherein X is Ni and y is between 20 and 80.
4. The disk of claim 1 further comprising a layer consisting of crystalline MgO between the MgXO layer and the magnetic recording layer, wherein the MgO layer is in contact with the MgOX layer and the magnetic recording layer is in contact with the MgO layer.
5. The disk of claim 1 wherein the magnetic recording layer is in contact with the MgXO layer and further comprising a layer consisting of crystalline MgO between the underlayer and the MgXO layer, wherein the MgXO layer is in contact with the MgO layer.
6. The disk of claim 1 wherein the underlayer comprises a seed layer for growth of the MgXO layer and wherein the MgXO layer is in contact with the seed layer.
7. The disk of claim 6 wherein the seed layer comprises a layer of a NiTa alloy.
8. The disk of claim 1 wherein the chemically-ordered alloy of the magnetic recording layer includes an element selected from the group consisting of Ni, Au, Cu, Pd and Ag.
9. The disk of claim 1 wherein the chemically-ordered alloy of the magnetic recording layer consists of the generally equiatomic binary FePt alloy.
10. The disk of claim 1 wherein the chemically-ordered alloy of the magnetic recording layer has a composition of the form FePt—Z, wherein the element Z is selected from the group consisting of Ni, Au, Cu, Pd and Ag.
11. The disk of claim 1 wherein the magnetic recording layer further comprises one or more segregants selected from SiO 2 , C, B, BN and a silicon nitride.
12. The disk of claim 1 wherein the underlayer comprises a layer of magnetically permeable material selected from alloys of CoNiFe, FeCoB, CoCuFe, NiFe, FeAlSi, FeTaN, FeN, FeTaC, CoTaZr, CoFeTaZr, CoFeB, and CoZrNb.
13. The disk of claim 1 wherein the underlayer comprises a heat sink layer.
14. The disk of claim 1 wherein the magnetic recording layer is patterned into discrete data islands of magnetizable material.
15. A thermally-assisted recording (TAR) magnetic recording disk drive comprising:
the TAR disk of claim 1 ;
a write head for applying a magnetic field to the magnetic recording layer;
an optical channel and near-field transducer for directing radiation to the magnetic recording layer; and
a read head for reading written data from the magnetic recording layer.
16. A thermally-assisted recording (TAR) disk comprising:
a substrate;
an insulating layer of a crystalline solid substitutional alloy having a composition of the form (Mg (100-y) Ni y )O, where y is between 20 and 80;
a seed layer between the substrate and the insulating layer and in contact with the insulating layer;
a magnetic recording layer comprising a chemically-ordered FePt alloy on and in contact with the insulating layer.
17. The disk of claim 16 further comprising a layer consisting of crystalline MgO between the insulating layer and the magnetic recording layer, wherein the MgO layer is in contact with the insulating layer and the magnetic recording layer is in contact with the MgO layer.
18. The disk of claim 16 wherein the magnetic recording layer is in contact with the insulating layer and further comprising a layer consisting of crystalline MgO between the substrate and the insulating layer, wherein the insulating layer is in contact with the MgO layer.
19. The disk of claim 16 wherein the chemically-ordered alloy of the magnetic recording layer is selected from the equiatomic binary FePt alloy and a pseudo-binary alloy having the formula (Fe(y)Pt(100-y))—Z, where y is between about 45 and 55 atomic percent and the element Z may be Ni, Au, Cu, Pd or Ag and is present in the range of between about 0% to about 20% atomic percent.
20. The disk of claim 16 wherein the magnetic recording layer further comprises one or more segregants selected from SiO 2 , C, B, BN and a silicon nitride.