Magnetic disk and method for manufacturing same
View Patent ↗Provided are a magnetic disk comprising a granular magnetic recording layer which causes less noise even with a recording capacity thereof of 250 G or more bits per square inch; and a method for manufacturing the same. The magnetic disk according to the present invention comprises: a granular magnetic recording layer ( 20 ) which is formed on a disk substrate 10 directly or via an intermediate layer and which has non-magnetic regions between granular columnar particles; and an auxiliary recording layer ( 22 ) which is formed on the granular magnetic recording layer 20 and which causes exchange interaction among the granular columnar particles, wherein the auxiliary recording layer ( 22 ) contains 0.1 to 3 moles of oxygen.
1. A magnetic disk comprising:
a disk substrate,
a magnetic recording layer disposed on said disk substrate and having a granular structure where non-magnetic grain boundary portions were formed between magnetic particles composed of CoCrPt and continuously growing in a columnar shape, said magnetic recording layer comprising a first main recording layer formed over the substrate and a second main recording layer formed over the first main recording layer;
an auxiliary recording layer formed on the magnetic recording layer; and
a separation layer comprising Ru or a Ru compound and having a thickness in the range of 0.1 nm to 1.0 nm and being disposed between the granular magnetic layer and the auxiliary layer,
wherein the auxiliary recording layer includes:
a non-granular auxiliary recording layer which is a magnetic layer almost magnetically continuous in the in-plane direction of the main surface of the disk substrate and comprises crystal grains having a larger cross sectional area than granular magnetic particles in the magnetic recording layer and having magnetic interaction with said granular magnetic particles; and
a granular auxiliary recording layer which is provided below the non-granular auxiliary recording layer, has higher coercive force than the non-granular auxiliary recording layer, and has a granular structure, and
wherein the granular auxiliary recording layer has a higher coercive force than the first main recording layer and the second main recording layer.
2. The magnetic disk according to claim 1 , wherein the auxiliary recording layer contains 0.1 to 3 mol % of oxygen, and
wherein the oxygen is contained in the auxiliary recording layer in a state of an oxide.
3. The magnetic disk according to claim 2 , wherein the oxide is a precipitate from the separation layer on the non-magnetic regions of the granular magnetic recording layer and Ru is a precipitate on the magnetic particles.
4. The magnetic disk according to any one of claims 2 , 3 and 1 , wherein the granular magnetic recording layer contains oxygen, and the amount of oxygen contained in the auxiliary recording layer is less than that in the granular magnetic recording layer.
5. The magnetic disk according to any one of claims 2 , 3 and 1 , wherein oxygen is contained in the granular magnetic recording layer and the oxygen has two or more kinds of oxides mixed therein.
6. The magnetic disk according to any one of claims 2 , 3 and 1 , wherein the separation layer is non-magnetic.
7. The magnetic disk according to any of claims 2 , 3 and 1 , wherein the magnetic recording layer comprises at least a third main recording layer.
8. The magnetic disk according to claim 1 , wherein the granular auxiliary recording layer has lower at % of Cr and higher at % of CoPt than the magnetic recording layer.
9. The magnetic disk according to claim 8 , wherein the difference (A−B) of a Cr concentration (A) of the magnetic recording layer and a Cr concentration (B) of the granular auxiliary recording layer is not less than 1 at % and not more than 4 at %.
10. The magnetic disk according to claim 1 or 8 , wherein the granular auxiliary recording layer has thinner film thickness than the non-granular auxiliary recording layer.
11. The magnetic disk according to claim 10 , wherein a thickness of the granular auxiliary recording layer is within a range of 0.5 nm to 5.0 nm and a thickness of the non-granular auxiliary recording layer is within a range of 4.0 nm-8.0 nm.
12. The magnetic disk according to claim 1 , wherein said separation layer further comprises oxides selected from the group consisting of oxides of W, Ti and Ru.
13. The magnetic disk according to claim 1 , wherein a thickness of the granular auxiliary recording layer is within a range of 0.5 nm to 5.0 nm and a thickness of the non-granular auxiliary recording layer is within a range of 4.0 nm-8.0 nm.
14. The magnetic disk according to claim 1 , wherein the auxiliary recording layer has a thickness in a range of 5 nm to 10 nm.