Patent ID: 8877359

Claim:
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.