Magnetic recording medium and magnetic memory device for high density recording
View Patent ↗A longitudinal magnetic recording medium having a high medium S/N, with no problems in view of the overwrite characteristic, excellent in the bit error rate and sufficiently stable also to thermal fluctuations is provided. In one embodiment, a first underlayer, second underlayer, and a third underlayer are formed on a substrate and, further, a first magnetic layer, a spacer layer including Ru as a main ingredient, a second magnetic layer, and a third magnetic layer are formed in adjacent with each other in this order. The thickness of the second magnetic layer is made larger than the thickness of the third magnetic layer and the total for the concentrations of cobalt and platinum obtained in the second magnetic layer is not more than the total for the concentrations of cobalt and platinum contained in the third magnetic layer.
1. A magnetic recording medium in which at least a first magnetic layer, a spacer layer comprising Ru as a main ingredient, a second magnetic layer, and a third magnetic layer are formed in contact with each other in order on a substrate, wherein a thickness of the second magnetic layer is larger than a thickness of the third magnetic layer and the total for the concentrations of cobalt and platinum contained in the second magnetic layer is not higher than the total for the concentrations of cobalt and platinum contained in the third magnetic layer;
wherein platinum is contained in the first magnetic layer, the second magnetic layer, and the third magnetic layer; and
wherein the concentration of platinum contained in the second magnetic layer is higher than the concentration of platinum contained in the first magnetic layer, and the concentration of platinum contained in the third magnetic layer is higher than the concentration of platinum contained in the second magnetic layer.
2. A magnetic recording medium according to claim 1 , wherein the total for the concentrations of cobalt and platinum contained in the second magnetic layer is from about 68 at. % to 76 at. %.
3. A magnetic recording medium according to claim 1 , wherein the first magnetic layer comprises an alloy containing Co—Cr, the second magnetic layer comprises an alloy containing Co—Cr—Pt—B, and the third magnetic layer comprises an alloy containing Co—Pt.
4. A magnetic recording medium according to claim 3 , wherein a first underlayer comprising one of a Co—Ti—Ni alloy other Co—Ti alloys and a Ni—Ta alloy, a second underlayer comprising a W—Co alloy or Ta, and a third underlayer comprising a Cr—Ti—B alloy or other Cr—Ti alloy are present between the substrate and the first magnetic layer.
5. A magnetic recording medium according to claim 1 , further comprising a fourth magnetic layer formed in contact with the third magnetic layer.
6. A magnetic recording medium according to claim 5 , wherein the total for the concentration of the ferromagnetic metal elements and the concentration of platinum containing in the second magnetic layer is not more than the total for the concentration of the ferromagnetic metal elements and the concentration of platinum containing in the third magnetic layer.
7. A magnetic recording medium according to claim 5 , wherein the total for the concentration of the ferromagnetic metal elements and the concentration of platinum contained in the third magnetic layer is not more than the total for the concentration of the ferromagnetic metal elements and the concentration of platinum contained in the fourth magnetic layer.
8. A magnetic recording medium according to claim 5 , wherein the thickness of the third magnetic layer is larger than the thickness of the fourth magnetic layer.
9. A magnetic memory device comprising:
a magnetic recording medium in which at least a first magnetic layer, a spacer layer comprising Ru as a main ingredient, a second magnetic layer, and a third magnetic layer are formed in contact with each other in order on a substrate, wherein a thickness of the second magnetic layer is larger than a thickness of the third magnetic layer and the total for the concentrations of cobalt and platinum contained in the second magnetic layer is not higher than the total for the concentrations of cobalt and platinum contained in the third magnetic layer;
a composite type head having a writing head and a magnetoresistive reading head for writing and reading data to and from the magnetic recording medium; and
a positioning mechanism confirmed to position the composite type head to a radial direction of the magnetic recording medium;
wherein platinum is contained in the first magnetic layer, the second magnetic layer, and the third magnetic layer of the magnetic recording medium; and
wherein the concentration of platinum contained in the second magnetic layer is higher than the concentration of platinum contained in the first magnetic layer, and the concentration of platinum contained in the third magnetic layer is higher than the concentration of platinum contained in the second magnetic layer in the magnetic recording medium.
10. A magnetic memory device according to claim 9 , wherein the total for the concentrations of cobalt and platinum contained in the second magnetic layer of the magnetic recording medium is from about 68 at. % to 76 at. %.
11. A magnetic recording medium according to claim 9 , wherein the first magnetic layer comprises an alloy containing Co—Cr, the second magnetic layer comprises an alloy containing Co—Cr—Pt—B, and the third magnetic layer comprises an alloy containing Co—Pt.
12. A magnetic recording medium according to claim 11 , wherein a first underlayer comprising one of a Co—Ti—Ni alloy other Co—Ti alloys and a Ni—Ta alloy, a second underlayer comprising a W—Co alloy or Ta, and a third underlayer comprising a Cr—Ti—B alloy or other Cr—Ti alloys are present between the substrate and the first magnetic layer.
13. A magnetic recording medium according to claim 9 , farther comprising a fourth magnetic layer formed in contact with the third magnetic layer.
14. A magnetic recording medium according to claim 13 , wherein the total for the concentration of the ferromagnetic metal elements and the concentration of platinum containing in the second magnetic layer is not more than the total for the concentration of the ferromagnetic metal elements and the concentration of platinum containing in the third magnetic layer.
15. A magnetic recording medium according to claim 13 , wherein the total for the concentration of the ferromagnetic metal elements and the concentration of platinum contained in the third magnetic layer is not more than the total for the concentration of the ferromagnetic metal elements and the concentration of platinum contained in the fourth magnetic layer.
16. A magnetic recording medium according to claim 13 , wherein the thickness of the third magnetic layer is larger than the thickness of the fourth magnetic layer.