Magnetic recording medium and magnetic storage apparatus

1. A magnetic recording medium comprising:

a substrate;

a magnetic recording layer made of a Co alloy or a CoCr alloy;

a seed layer disposed between the substrate and the magnetic recording layer; and

an underlayer made of a group selected from one of RuAl, VAl, MnRh, IrAl and OsAl, and disposed between the seed layer and the magnetic recording layer,

said seed layer is made of a material consisting only of one of the elements forming the binary alloy material of the underlayer.

2. The magnetic recording medium as claimed in claim 1 , wherein said magnetic recording layer is made up of a single magnetic layer or a synthetic ferrimagnetic structure, said synthetic ferrimagnetic structure being made up of at least two antiferromagnetically coupled CoCr alloy magnetic layers, wherein c-axes of CoCr alloy magnetic layers are significantly parallel to a film plane thereof such that a ratio h≦0.15, where h=Hc⊥/Hc, Hc⊥ denotes perpendicular coercivity, and Hc denotes coercivity along the film plane.

3. The magnetic recording medium as claimed in claim 1 , wherein when said underlayer is made of a material selected from a group consisting of RuAl, MnRh, IrAl and OsAl, the underlayer has approximately 40% to 60% composition ranges of one of the elements forming the binary alloy material.

4. The magnetic recording medium as claimed in claim 1 , wherein said underlayer has a thickness of approximately 5 nm to 60 nm.

5. The magnetic recording medium as claimed in claim 1 , wherein said seed layer has a thickness of approximately 0.5 nm to 50 nm.

6. The magnetic recording medium as claimed in claim 1 , wherein a total thickness of said seed layer and said underlayer is in a range of approximately 30 nm to 60 nm.

7. The magnetic recording medium as claimed in claim 1 , wherein said substrate is mechanically textured.

8. The magnetic recording medium according to claim 1 , further comprising:

a Cr—M lattice matching layer having a thickness of approximately 1 nm to 10 nm formed directly on said underlayer and disposed between said underlayer and said magnetic recording layer, where M is a material selected from a group consisting of Mo, Ti, V, and W of atomic proportion greater than or equal to 10%.

9. The magnetic recording medium as claimed in claim 8 , further comprising:

an interlayer made of a hcp structured CoCr alloy having a thickness of approximately 1 nm to 5 nm and disposed between said Cr—M lattice matching layer and said magnetic recording layer.

10. The magnetic recording medium as claimed in claim 1 , further comprising:

an interlayer made of a hcp structured CoCr alloy having a thickness of approximately 1 nm to 5 nm and disposed between said underlayer and said magnetic recording layer.

11. The magnetic recording medium as claimed in claim 1 , further comprising:

a lattice matching layer made essentially of Ru having a thickness of approximately 1 nm to 3 nm in direct contact with said magnetic recording layer and disposed between said underlayer and said magnetic recording layer.

12. A magnetic storage apparatus comprising:

at least one magnetic recording medium comprising a substrate, a magnetic recording layer made of a Co alloy or a CoCr alloy, a seed layer disposed between the substrate and the magnetic recording layer, and an underlayer made of a group selected from one of RuAl, VAl, MnRh, IrAl and OsAl, and disposed between the seed layer and the magnetic recording layer, said seed layer being made of a material consisting only of one of the elements forming the binary alloy material of the underlayer; and

a head which writes information on and/or reproduces information from the magnetic recording medium.

13. The magnetic storage apparatus as claimed in claim 12 , wherein the underlayer of said magnetic recording medium is made of a material selected from a group consisting of RuAl, MnRh, IrAl and OsAl, the underlayer has approximately 40% to 60% composition ranges of one of the elements forming the binary alloy material.

14. The magnetic storage apparatus as claimed in claim 12 , wherein said magnetic recording medium is a magnetic disk.