Magnetic recording medium, magnetic storage apparatus and method of producing magnetic recording medium
View Patent ↗A magnetic recording medium is provided with an hcp Co alloy magnetic layer with the crystallographic c-axes tilted at an angle from a substrate surface and fixed relative to a recording direction. The tilt is induced by epitaxial growth of the hcp Co alloy on an obliquely evaporated nonmagnetic polycrystalline underlayer, so that the magnetic recording medium exhibits thermal stability and improved overwrite with a single pole-type head.
1. A perpendicular magnetic recording medium comprising:
a substrate;
an hcp Co-based magnetic layer;
an hcp underlayer provided on the substrate with c-axes tilted at an angle between 10° to 45° from a substrate normal with a distribution at said angle being less than 5°,
wherein said magnetic layer is grown epitaxially on said underlayer and in a vertical columnar fashion, and said magnetic layer includes at least a first magnetic layer provided on said underlayer and a second magnetic layer disposed above said first magnetic layer;
an amorohous seed layer, having a thickness of at least 1 nm, disposed between said underlayer and said substrate; and
a spacer layer made of a material selected from a group consisting of Ru, Re, Os, Ir, and alloys thereof and disposed between said first and second magnetic layers so that antiparallel coupling is induced between said first and second magnetic layers,
wherein said amorohous seed layer includes one or a plurality of antiferromagnetic layers.
2. The perpendicular magnetic recording medium as claimed in claim 1 , further comprising:
a soft magnetic layer, having a thickness of 50 nm to 400 nm, disposed between said underlayer and said substrate.
3. The perpendicular magnetic recording medium as claimed in claim 1 , wherein said underlayer is made of a material selected from a group consisting of Os, Re, Ru, nonmagnetic CoCr, and nonmagnetic CoCr-M, where M is selected from a group consisting of Os, Re, Ru, and Ta.
4. The perpendicular magnetic recording medium as claimed in claim 1 , wherein at least one of said first and second magnetic layers is made of a material selected from a group consisting of CoCrPt, CoCrPtB, CoCrPtBCu, CoCrPt—O, CoCrPt—SiO 2 .
5. The perpendicular magnetic recording medium as claimed in claim 1 , wherein said hcp underlayer has a thickness of 2 nm to 20 nm.
6. The perpendicular magnetic recording medium as claimed in claim 2 , further comprising:
an amorphous seed layer, having a thickness of at least 1 nm, disposed between said underlayer and said soft magnetic layer.
7. The perpendicular magnetic recording medium as claimed in claim 1 , further comprising:
an fcc layer, disposed between said underlayer and said substrate, in direct contact with said underlayer and having a thickness of 1 nm to 5 nm.
8. A magnetic storage apparatus comprising:
at least one perpendicular magnetic recording medium; and
a transducer writing information on and/or reading information from said magnetic recording medium;
said perpendicular magnetic recording medium comprising:
a substrate;
an hcp Co-based magnetic layer;
an hcp underlayer provided on the substrate with c-axes tilted at an angle between 10° to 45° from a substrate normal with a distribution at said angle being less than 5°, wherein said magnetic layer is grown epitaxially on said underlayer and in a vertical columnar fashion, and said magnetic layer includes at least a first magnetic layer provided on said underlayer and a second magnetic layer disposed above said first magnetic layer;
an amorphous seed layer, having a thickness of at least 1 nm, disposed between said underlayer and said substrate; and
a spacer layer made of a material selected from a group consisting of Ru, Re, Os, Ir, and alloys thereof and disposed between said first and second magnetic layers so that antiparallel coupling is induced between said first and second magnetic layers,
wherein said amorphous seed aver of said perpendicular magnetic recording medium includes one or a pluralitv of antiferromagnetic layers.
9. The magnetic storage apparatus as claimed in claim 8 , wherein said perpendicular magnetic recording medium further comprises:
a soft magnetic layer, having a thickness 50 nm to 400 nm, disposed between said underlayer and said substrate.
10. The magnetic storage apparatus as claimed in claim 8 , wherein said underlayer of said perpendicular magnetic recording medium is made of a material selected from a group consisting of Os, Re, Ru, nonmagnetic CoCr, and nonmagnetic CoCr-M, where M is selected from a group consisting of Os, Re, Ru, and Ta.
11. The magnetic storage apparatus as claimed in claim 9 , wherein said perpendicular magnetic recording medium further comprises:
an amorphous seed layer, having a thickness of at least 1 nm, disposed between said underlayer and said soft magnetic layer.