Magnetic recording medium and method of manufacturing the same

1. A method of manufacturing a magnetic recording medium comprising:

directly texturing a surface of a non-magnetic substrate made of a glass material to form circular concentric grooves thereon;

forming a seed layer on the non-magnetic substrate;

forming an under layer on the seed layer;

forming a magnetic layer on the under layer; and

forming a protective layer on the magnetic layer, wherein

the textured non-magnetic substrate has at least five circular concentric grooves per 1 square um span on the surface thereof, and has an average surface roughness Ra of 0.2 to 1 nm,

exposing the seed layer to a mixed gas comprising an inert gas and oxygen prior to forming the under layer, and

a ratio of an in-plane remanent magnetization in a circumferential direction of the magnetic recording medium to an in-plane remanent magnetization in a radial direction of the magnetic recording medium is equal to or greater than 1.05.

2. The method of manufacturing a magnetic recording medium according to claim 1 , wherein a slurry comprises abrasive grains comprising at least one of diamond, aluminum oxide, cerium oxide, silicon carbide, and colloidal silica to texture the non-magnetic substrate.

3. The method of manufacturing a magnetic recording medium according to claim 2 , wherein the abrasive grains have a mean particle diameter of 0.01 to 2 μm.

4. The method of manufacturing a magnetic recording medium according to claim 2 , wherein the abrasive grains in the slurry have a concentration of 0.01 to 5 weight %.

5. The method of manufacturing a magnetic recording medium according to claim 1 , wherein a machining pad excluding abrasive grains and made of a material comprising at least one of urethane, polyester, and nylon is forced against the non-magnetic substrate, where the machining pad rubs the non-magnetic substrate.

6. The method of manufacturing a magnetic recording medium according to claim 5 , wherein the machining pad comprises a woven cloth produced by weaving extra fine fibers with a diameter of less than or equal to 10 μm, and a raised cloth formed by raising the woven cloth.

7. The method of manufacturing a magnetic recording medium according to claim 5 , wherein the machining pad is forced against the non-magnetic substrate with a pressure of 9.8 to 196 kPa.

8. The method of manufacturing a magnetic recording medium according to claim 1 , wherein the mixed gas comprises the oxygen of at least 0.7 volume %.

9. The method of manufacturing a magnetic recording medium according to claim 1 , further comprising:

exposing the seed layer to a mixed gas comprising an inert gas and air prior to forming the under layer, wherein the mixed gas comprises the air of at least 2 volume %.

10. The method of manufacturing a magnetic recording medium according to claim 1 , further comprising:

exposing the seed layer to a mixed gas comprising an inert gas, nitrogen, and oxygen prior to forming the under layer, wherein the mixed gas comprises the nitrogen of at least 1.6 volume % and the oxygen of at least 0.4 volume %.

11. A method of manufacturing a magnetic recording medium comprising:

directly texturing a surface of a non-magnetic substrate made of a glass material to form circular concentric grooves thereon;

forming a seed layer on the non-magnetic substrate;

forming an under layer on the seed layer;

forming a magnetic layer on the under layer; and

forming a protective layer on the magnetic layer, wherein

the textured non-magnetic substrate has at least five circular concentric grooves per 1 square μm span on the surface thereof, and has an average surface roughness Ra of 0.2 to mm

a ratio of an in-plane remanent magnetization in a circumferential direction of the magnetic recording medium to an in-plane remanent magnetization in a radial direction of the magnetic recording medium is equal to or greater than 1.05, and the forming of the seed layer further comprises forming a portion at a depth of 0.8 to 3 nm from a surface of the seed layer by reactive sputtering in a mixed gas comprising oxygen of at least 1% in inert gas.

12. The method of manufacturing a magnetic recording medium according to claim 11 , wherein the forming of the seed layer further comprises forming a portion at a depth of 0.8 to 3 nm from a surface of the seed layer by reactive sputtering in a mixed gas comprising air of at least 3% in inert gas.

13. The method of manufacturing a magnetic recording medium according to claim 11 , wherein the forming of the seed layer further comprises forming a portion at a depth of 0.8 to 3 nm from a surface of the seed layer by reactive sputtering in a mixed gas comprising nitrogen of at least 2.4% and oxygen of at least 0.6% in inert gas.

14. The method of manufacturing a magnetic recording medium according to claim 1 , wherein the seed layer comprises NiP.

15. The method of manufacturing a magnetic recording medium according to claim 14 , wherein the NIP contains P of 19 to 33 atomic %.

16. The method of manufacturing a magnetic recording medium according to claim 14 , wherein the seed layer has a thickness of 5 to 28 nm.

17. The method of manufacturing a magnetic recording medium according to claim 1 , wherein the under layer comprises a first under layer and a second under layer, the first under layer having a thickness of 3 to 8 nm and the second under layer having a thickness of 1 to 8 nm.