Manufacturing method of glass substrate for magnetic disk, magnetic disk, and magnetic recording / reproducing device

1. A manufacturing method of a glass substrate for a magnetic disk, comprising:

polishing a principal face of the glass substrate using a slurry containing zirconium oxide abrasive grains, each of the abrasive grains having zirconium oxide as a principal component, with the zirconium oxide in each of the abrasive grains having crystallites of monoclinic crystalline structures and crystallites of tetragonal crystalline structures as an abrasive, and in each of the zirconium oxide abrasive grains, a ratio of the amount of the tetragonal crystalline structures with respect to the amount of the monoclinic crystalline structures falls in a range of 0.7% to 3.0%, where the ratio is obtained by x-ray diffraction and is defined as a ratio of a peak intensity of the tetragonal crystalline structures with respect to a peak intensity of the monoclinic crystalline structures, and the peak intensity is defined as an integrated peak intensity.

2. The manufacturing method of a glass substrate for a recited in claim 1 , wherein the zirconium oxide abrasive grains are made of aggregates of primary particles of zirconium oxide and the primary particles of zirconium oxide have crystallites of the monoclinic crystalline structures and crystallites of the tetragonal crystalline structures.

3. The manufacturing method of a glass substrate for a magnetic disk recited in claim 1 , wherein the zirconium oxide abrasive grains do not contain stabilizing agent.

4. The manufacturing method of a glass substrate for a magnetic disk recited in claim 1 , wherein the average particle size D50 of the zirconium oxide abrasive grains is set to be in a range of 0.2 to 0.5 μm.

5. The manufacturing method of a glass substrate for a magnetic disk recited in claim 1 , wherein a polisher pad is used for polishing a principal face of the glass substrate in the polishing, the polisher pad having hardness in a range of 80 to 100 in JIS-A hardness.

6. The manufacturing method of a glass substrate for a magnetic disk recited in claim 1 , wherein the glass substrate is made of glass, the glass having the fracture toughness value in a range of 0.4 to 1.5 MPa·m 1/2 .

7. The manufacturing method of a glass substrate for a magnetic disk recited in claim 1 , further comprising:

after the polishing, performing a post polishing using a slurry containing colloidal silica as abrasive grains.

8. The manufacturing method of a glass substrate for a magnetic disk recited in claim 7 , wherein a removal stock is set to be less than or equal to 5 μm in the post polishing.

9. The manufacturing method of a glass substrate for a magnetic disk recited in claim 7 , further comprising:

an intermediate polishing using a slurry containing cerium oxide abrasive grains, the intermediate polishing being performed between the polishing and the post polishing.

10. The manufacturing method of a glass substrate for a magnetic disk recited in claim 7 , further comprising:

a chemically strengthening process performed between the polishing and the post polishing.

11. A magnetic disk made of a glass substrate manufactured with the method recited in claim 1 , wherein at least a magnetic layer is formed on a principal face of the glass substrate.

12. A magnetic recording/reproducing device, comprising:

the magnetic disk recited in claim 11 ; and

a magnetic head embedded with a DFH (Dynamic Flying Height) control mechanism.

13. The manufacturing method of a glass substrate for a magnetic disk recited in claim 1 , wherein the zirconium oxide abrasive grains are obtained by sintering zirconium oxide formed by the monoclinic crystalline structures substantially at a temperature that begins phase transition from the monoclinic crystalline structures to the tetragonal crystalline structures.