Method of producing a magnetic recording medium and a magnetic recording medium formed thereby
View Patent ↗A perpendicular magnetic recording medium has a magnetic recording layer with ferromagnetic crystalline grains and nonmagnetic and nonmetallic grain boundary region surrounding the grains. The surface of its underlayer, before forming the magnetic recording layer, is exposed to an O 2 or N 2 atmosphere or an atmosphere of rare gas and O 2 or N 2 , to attach the O 2 or N 2 as nucleation sites for promoting growth of the nonmagnetic and nonmetallic region. By forming the magnetic recording layer thereafter, both ferromagnetic crystalline grains and the nonmagnetic and nonmetallic grain boundary region are formed from the initial stage of the growth of the magnetic recording layer. Thus, a magnetic recording layer having excellent segregation structure can be formed.
1. A method of producing a perpendicular magnetic recording medium comprising the steps of:
forming an underlayer over a nonmagnetic substrate;
attaching O 2 or N 2 to the underlayer after the underlayer has been fully formed; and then
forming a magnetic recording layer on the underlayer, wherein the magnetic recording layer comprises ferromagnetic crystalline grains and nonmagnetic grain boundary region composed mainly of oxide or nitride surrounding the crystalline grains.
2. A method of producing a perpendicular magnetic recording medium according to claim 1 , wherein the O 2 or N 2 is attached to the underlayer in an atmosphere-containing a rare gas.
3. A method of producing a perpendicular magnetic recording medium according to claim 1 , wherein the underlayer is composed of Ru or a Ru alloy.
4. A method of producing a perpendicular magnetic recording medium according to claim 3 , wherein the Ru alloy is RuW, RuCu, RuC, RuB, or RuCoCr.
5. A method of producing a perpendicular magnetic recording medium according to claim 1 , further comprising the step of forming a seed layer before forming the underlayer, the seed layer being composed of a Ni-base alloy.
6. A method of producing a perpendicular magnetic recording medium according to claim 5 , wherein the Ni-base alloy is NiFe, NiFeNb, NiFeB, NiFeSi, or NiFeCr.
7. A method of producing a perpendicular magnetic recording medium according to claim 5 , further comprising the step of forming a soft magnetic underlayer.
8. A method of producing a perpendicular magnetic recording medium according to claim 7 , wherein the soft magnetic underlayer is composed of crystalline materials of a NiFe alloy and a Sendust alloy (FeSiAl), fine crystalline materials of FeTaC and CoTaZr, or an amorphous cobalt alloy of CoZrNb.
9. A method of producing a perpendicular magnetic recording medium according to claim 1 , wherein the underlayer is crystalline having a face centered cubic structure or hexagonal closest packed structure.
10. A method of producing a perpendicular magnetic recording medium according to claim 1 , further comprising the steps of forming a protective layer on the magnetic recording layer, and then forming a liquid lubricant layer on the protective layer.
11. A method of producing a perpendicular magnetic recording medium according to claim 1 , wherein the O 2 or N 2 is attached to the underlayer by exposing the underlayer to an argon gas containing O 2 or N 2 for 10 seconds.
12. A perpendicular magnetic recording medium produced by the method according to claim 1 .
13. A perpendicular magnetic recording medium produced by the method according to claim 2 .
14. A perpendicular magnetic recording medium produced by the method according to claim 3 .
15. A perpendicular magnetic recording medium produced by the method according to claim 4 .
16. A perpendicular magnetic recording medium produced by the method according to claim 5 .
17. A perpendicular magnetic recording medium produced by the method according to claim 6 .
18. A perpendicular magnetic recording medium produced by the method according to claim 7 .
19. A perpendicular magnetic recording medium produced by the method according to claim 8 .