Soft underlayer for heat assisted magnetic recording media
View Patent ↗A soft underlayer (SUL) and methods for making an SUL are provided, the SUL having characteristics that make it compatible with the high temperature requirements associated with heat-assisted magnetic recording (HAMR) media growth and writing, e.g., temperatures greater than 500° C. The SUL may have a high crystallization temperature of greater than 450° C. and a high Curie temperature greater than 300° C., for example. Additionally, the SUL can maintain a saturation magnetization value greater than, e.g., 9 kGauss, at such high temperatures, thereby having the ability to remain amorphous at temperatures up to, e.g., 650° C., and exhibiting a relatively flat integrated noise profile from approximately 300° C. to 650° C. Further still, a spacer layer material is chosen such that inter-diffusion does not occur at these high temperatures.
1. A recording medium, comprising:
a magnetic recording layer;
a soft underlayer disposed under the magnetic recording layer, the soft underlayer comprising:
a first soft underlayer portion formed of a first soft underlayer material comprising a Cobalt-Iron (CoFe) material having a set of additives, the set of additives comprising W; and
a second soft underlayer portion formed of a second soft underlayer material wherein the second underlayer material is different from the first underlayer material,
wherein the first and second soft underlayer materials have Curie temperatures exceeding 300° C. and saturation magnetization values greater than 9 kGauss, and wherein the second soft underlayer material maintains an amorphous microstructure at a temperature greater than 450° C., wherein material composition ranges of the first and second soft underlayer materials comprise 20 to 90% Cobalt (Co), at most 60% Iron (Fe), at most 20% Nickel (Ni), at most 20% Zirconium (Zr), at most 15% Boron (B), at most 20% Tantalum (Ta), at most 10% Tungsten (W), and at most 10%_Molybdenum (Mo); and
a spacer layer disposed between the first and second soft undeclayer portions, the spacer layer comprising material having inter-diffusion-resistant properties at temperatures greater than 1800° C., wherein the spacer layer is composed of one of Niobium (Nb), Vanadium (V), Mo, Osmium (Os), Carbon (C), Magnesium-Oxide (MgO), W, Rhenium (Re), Titanium Nitride (TiN), TiC, VN, MoC, TaN, TaC, Zr0 2 , Yttrium Oxide (Y 2 0 3 ), Silicon Dioxide (Si0 2 ), or Ta;
an adhesion layer; and
a heatsink layer configured to facilitate heat transfer for the recording medium, wherein the soft underlayer and heatsink layer are disposed over the adhesion layer and under the magnetic recording layer.
2. The recording medium of claim 1 , further comprising an interlayer disposed over the soft underlayer, an overcoat disposed over the magnetic recording layer, a lubricant disposed over the overcoat, and a substrate disposed under the adhesion layer, wherein the heatsink layer is disposed between the interlayer and soft underlayer.
3. The recording medium of claim 2 , wherein the substrate comprises one of a glass substrate, a metal substrate, a metal alloy substrate, a polymer substrate, or a ceramic substrate.
4. The recording medium of claim 1 , further comprising an interlayer disposed under the magnetic recording layer and over the soft underlayer, an overcoat disposed over the magnetic recording layer, a lubricant disposed over the overcoat, and a substrate disposed under the adhesion layer, wherein the heatsink layer is disposed between the soft underlayer and adhesion layer.
5. The recording medium of claim 4 , wherein the substrate comprises one of a glass substrate, a metal substrate, a metal alloy substrate, a polymer substrate, or a ceramic sub.
6. The recording medium of claim 1 further comprising at least one additional soft underlayer, the at least one additional soft underlayer comprising additional first and second soft underlayer materials between which an additional spacer layer is disposed.
7. The recording medium of claim 1 , wherein the spacer layer has a melting temperature greater than 1800° C.
8. The recording medium of claim 1 , wherein the set of additives further comprises B and Ta.
9. The recording medium of claim 1 , wherein the set of additives further comprises B and Zr.
10. The recording medium of claim 9 , wherein the set of additives further comprises Ta.
11. The recording medium of claim 10 , wherein the second soft underlayer material comprises Co and Fe.