Dynamic spring media with multiple exchange coupled hard-soft magnetic layers
View Patent ↗A perpendicular magnetic recording (PMR) media structure with multiple exchange couple composite (ECC) layer structure is described. The PMR disk structure may include multiple soft magnetic layers with intervening hard magnetic layers and in between. The interface between the soft magnetic layers and the hard magnetic layers may be separated by exchange coupled layers.
1. A perpendicular magnetic recording disk, comprising:
a substrate;
a first hard magnetic layer disposed above the substrate;
a lower soft magnetic layer disposed between the substrate and the first hard magnetic layer, the first hard magnetic layer being disposed closer to the substrate than any other hard magnetic layer;
a soft magnetic underlayer in contact with the lower soft magnetic layer and disposed between the substrate and the lower soft magnetic layer;
a first exchange coupling layer disposed between the lower soft magnetic layer and the first hard magnetic layer;
a middle soft magnetic layer disposed above the first hard magnetic layer;
a second hard magnetic layer disposed above the middle soft magnetic layer;
a second exchange coupling layer disposed between the first hard magnetic layer and the middle soft magnetic layer;
a third exchange coupling layer disposed between the middle soft magnetic layer and the second hard magnetic layer;
a fourth exchange coupling layer disposed above the second hard magnetic layer; and
an upper soft magnetic layer disposed above the fourth exchange coupling layer.
2. The perpendicular magnetic recording disk of claim 1 , wherein a second anisotropy field of the middle soft magnetic layer is greater than a first anisotropy field of the lower soft magnetic layer.
3. The perpendicular magnetic recording disk of claim 1 , wherein a third anisotropy field of upper soft magnetic layer is greater than the second anisotropy field of the middle soft magnetic layer.
4. The perpendicular magnetic recording disk of claim 1 , wherein a lateral exchange coupling in each of the soft magnetic layers is approximately 0.2 μerg/cm, and wherein a coupling across each of the exchange coupling layers is on the order of 1 erg/cm 2 .
5. The perpendicular magnetic recording disk of claim 1 , wherein the first and second hard magnetic layers are ferromagnetic layers.
6. The perpendicular magnetic recording disk of claim 1 , wherein a lateral exchange coupling in each of the hard magnetic layers is 0.1 uerg/cm.
7. The perpendicular magnetic recording disk of claim 1 , wherein an anisotropy field of each of the hard magnetic layers is greater than 10 kOe.
8. The perpendicular magnetic recording disk of claim 7 , wherein an anisotropy field of each of the soft magnetic layers is less than 10 kOe.
9. The perpendicular magnetic recording disk of claim 8 , further comprising a seed layer disposed between the soft magnetic underlayer and the substrate.
10. The perpendicular magnetic recording disk of claim 8 , wherein the anisotropy field of each of the soft magnetic layers is between 4 kOe and less than 10 kOe.
11. The perpendicular magnetic recording disk of claim 10 , wherein the anisotropy field of each of the soft magnetic layers is 8 kOe.
12. The perpendicular magnetic recording disk of claim 10 , wherein an anisotropy field of each of the hard magnetic layers is between 12 kOe and 20 kOe.
13. The perpendicular magnetic recording disk of claim 12 , wherein an anisotropy field of each of the hard magnetic layers is 18 kOe.
14. The perpendicular magnetic recording disk of claim 13 , wherein each of the hard magnetic layers has a thickness between 6 nanometers (nm) and 12 nm.
15. The perpendicular magnetic recording disk of claim 14 , wherein the thickness of each of the hard magnetic layers is 10 nm.
16. The perpendicular magnetic recording disk of claim 15 , wherein a saturation magnetization for each of the hard magnetic layers and soft magnetic layers is between 500 emu/cc and 700 emu/cc.
17. The perpendicular magnetic recording disk of claim 16 , wherein the saturation magnetization for each of the hard magnetic layers and soft magnetic layers is 600 emu/cc.
18. The perpendicular magnetic recording disk of claim 17 , wherein each of the soft magnetic layers has a thickness between 3 nm and 6 nm.