Magnetic recording medium
View Patent ↗Provided is a magnetic recording medium which maintains high S/N ratio and coercive force (Hc) and has high recording density, even with fine magnetic particles, by further improving crystal orientation of a magnetic recording layer. The magnetic recording medium is provided with an orientation control layer ( 16 ), a nonmagnetic under layer ( 18 ), and a magnetic recording layer ( 22 ) on a substrate. The orientation control layer ( 16 ) has an fcc structure and a (111) plane parallel to the substrate. The under layer ( 18 ) has an hcp structure and a (0001) plane parallel to the substrate. An atomic distance of the (111) plane of the orientation control layer ( 16 ) is −0.2 Å to +0.15 Å to a lattice spacing of the under layer ( 18 ).
1. A perpendicular magnetic recording medium with recording density higher than 150 Gbits per square inch, comprising:
an orientation control layer, a non-magnetic under layer, a magnetic recording layer on a substrate, wherein
the orientation control layer has an fcc structure and a (111) plane being parallel to the substrate;
the under layer comprises two layers, said layers differing in crystalline characteristics, and has an hcp structure and a (0001) plane being parallel to the substrate;
the magnetic recording layer has an hcp structure and a (0001) plane being parallel to the substrate; and
a difference of the distance between nearest-neighbor atoms of the orientation control layer from the distance between nearest-neighbor atoms on a (0001) plane of the under layer is from −0.2 Å to +0.15 Å,
wherein the orientation control layer is made of an alloy including Ni as a main component and 5 to 20 at % of one or more of Ti, V, Ta, Cr, Mo, and W as an addition element.
2. The magnetic recording medium according to claim 1 , wherein the under layer is selected from Ru, RuCr, and RuCo.
3. The magnetic recording medium according to claim 1 , wherein the magnetic recording layer is a ferromagnetic layer of a granular structure formed by segregating a non-magnetic material among magnetic particles containing at least Co.
4. The magnetic recording medium according to claim 1 , wherein the recording layer comprises two layers that differ in thickness.
5. The magnetic recording medium according to claim 4 , wherein the thickness of a larger layer is more than double a thickness of a smaller layer.
6. The magnetic recording medium according to claim 1 , wherein the atomic distance on the (111) plane is in the range of 2.51 and 2.53 inclusive.
7. The magnetic recording medium according to claim 1 , wherein the difference is in the range between −0.20 and −0.17 inclusive.
8. The magnetic recording medium according to claim 4 , wherein the two layers comprise a larger layer and a smaller layer and a thickness of the larger layer is substantially more than a thickness of the smaller layer.
9. The magnetic recording medium according to claim 4 , wherein the larger layer and the smaller layer comprise different materials.
10. The magnetic recording medium according to claim 1 , wherein, said two layers differ in crystal lattice size.
11. The magnetic recording medium according to claim 4 , wherein the larger layer is located between the smaller layer and the underlayer.