Magnetic recording medium substrate and perpendicular magnetic recording medium
View Patent ↗A perpendicular magnetic recording medium comprising a pair of soft magnetic layers that are laminated via a non-magnetic layer and antiparallel-coupled to each other and that are provided between a non-magnetic substrate and a magnetic recording layer, wherein spike noise and medium noise can be positively suppressed when information recording and reproduction are carried out at high recording surface density. At least one pair of soft magnetic layers are laid and formed via a non-magnetic layer on a substrate of a non-magnetic material so that magnetic characteristics obtained by integrating the pair of soft magnetic layers have a magnetic hysteresis to thereby prevent the formation of a magnetic domain wall.
1. A magnetic recording medium substrate comprising:
a substrate made of a nonmagnetic material, and
an underlayer formed on said substrate,
wherein, said underlayer comprises at least a pair of soft magnetic layers laminated through a nonmagnetic layer therebetween and has a magnetic hysteresis,
wherein said pair of soft magnetic layers are formed to have magnetic properties substantially equal to each other,
wherein a thickness of each of said soft magnetic layers is less than 55 nm and one of said layers has a thickness different from that of the other layer, and
wherein a difference between said thicknesses is 10 nm or less.
2. A magnetic recording medium substrate according to claim 1 , characterized in that
said soft magnetic layers are magnetically antiparallel-coupled to each other.
3. A perpendicular magnetic recording medium comprising:
a substrate made of a nonmagnetic material,
an underlayer formed on said substrate, and
a recording layer formed on said underlayer
wherein, said underlayer comprises at least a pair of soft magnetic layers laminated through a nonmagnetic layer therebetween and has a magnetic hysteresis,
wherein said pair of soft magnetic layers are formed to have magnetic properties substantially equal to each other,
wherein one of said layers has a thickness different from that of the other layer, and
wherein a difference between said thicknesses is 10 nm or less.
4. A perpendicular magnetic recording medium according to claim 3 characterized in that
said pair of soft magnetic layers are amorphous.
5. A perpendicular magnetic recording medium according to claim 3 , wherein said soft magnetic layers are magnetically antiparallel-coupled to each other.
6. A magnetic recording medium substrate according to claim 1 , wherein a soft magnetic layer comprises Co, Zr and Ta.
7. A magnetic recording medium substrate according to claim 1 , wherein said non-magnetic layer has a thickness of less than 0.9 nm.
8. A magnetic recording medium substrate according to claim 1 , wherein said non-magnetic layer comprises Ru.
9. A perpendicular magnetic recording medium according to claim 3 , wherein a soft magnetic layer comprises Co, Zr and Ta.
10. A perpendicular magnetic recording medium according to claim 3 , wherein said non-magnetic layer has a thickness of less than 0.9 nm.
11. A perpendicular magnetic recording medium according to claim 3 , wherein said non-magnetic layer comprises Ru.
12. A perpendicular magnetic recording medium according to claim 3 , wherein said medium has an areal information recording density of 100 GHbits/inch 2 or more.
13. A perpendicular magnetic recording medium according to claim 3 , wherein a magnetic domain is formed that is continuous over substantially an entire surface of the perpendicular magnetic recording medium.