Perpendicular magnetic recording medium and process for manufacture thereof
View Patent ↗An object of the present invention is to provide a perpendicular magnetic recording medium 100 including a magnetic recording layer 122 , the medium in which a particle diameter of crystal grains in the magnetic recording layer 122 of a two-layer structure is so designed as to improve an SNR while a high coercive force is maintained. In a method of manufacturing the perpendicular magnetic recording medium 100 according to the present invention, the perpendicular magnetic recording medium 100 includes at least a ground layer 118 , a first magnetic recording layer 122 a , and a second magnetic recording layer 122 b in this order on a disk base 110 ; the first magnetic recording layer 122 a and the second magnetic recording layer 122 b are ferromagnetic layers each having a granular structure in which a grain boundary part made of a non-magnetic substance is formed between crystal grains each grown in a columnar shape, and A<B when an average particle diameter of the crystal grains in the first magnetic recording layer 122 a is taken as A nm and an average particle diameter of the crystal grains in the second magnetic recording layer 122 b is taken as B nm.
1. A perpendicular magnetic recording medium comprising:
a base,
at least a ground layer,
a non-magnetic granular layer on the ground layer,
a first magnetic recording layer, and
a second magnetic recording layer, said layers being provided in this order on the base, wherein
the first magnetic recording layer and the second magnetic recording layer are ferromagnetic layers of a granular structure in which grain boundary parts made of a non-magnetic substance are each formed between crystal grains each grown in a columnar shape,
A<B when an average particle diameter of the crystal grains in the first magnetic recording layer is taken as A nm and an average particle diameter of the crystal grains in the second magnetic recording layer is taken as B nm, and
the average particle diameter of the non-magnetic granular layer is smaller than the average particle diameter of the first magnetic recording layer.
2. The perpendicular magnetic recording medium according to claim 1 wherein the non-magnetic granular layer includes non-magnetic crystal grains made of a Co alloy and a grain boundary part that comprises at least one of SiOx, Cr, CrO 2 , TiO 2 , ZrO 2 and Ta 2 O 5 .
3. The perpendicular magnetic recording medium, according to claim 1 , wherein
a ratio between the average particle diameter of the crystal grains in the first magnetic recording layer and the average particle diameter of the crystal grains in the second magnetic recording layer is 0.8<A/B<1.
4. The perpendicular magnetic recording medium according to claim 3 , wherein
a total thickness of the first magnetic recording layer and the second magnetic recording layer is equal to or smaller than 15 nm.
5. The perpendicular magnetic recording medium according to claim 3 , wherein
the non-magnetic substance includes any of chrome, oxygen, or an oxide, or a plurality thereof.
6. The perpendicular magnetic recording medium according to claim 5 wherein
the oxide includes one or a plurality of oxides selected from the group of SiO 2 , TiO 2 , Cr 2 O 3 , Ta 2 O 5 , Nb 2 O 5 , B 2 O 3 , and ZrO 2 .
7. The perpendicular magnetic recording medium according to claim 5 , wherein
an oxide included in the second magnetic recording layer includes one or a plurality of oxides selected from the group of SiO 2 , TiO 2 , Cr 2 O 3 , Ta 2 O 5 , Nb 2 O 5 , B 2 O 3 , and ZrO 2 .
8. The perpendicular magnetic recording medium according to claim 1 , wherein
a total thickness of the first magnetic recording layer and the second magnetic recording layer is equal to or smaller than 15 nm.
9. The perpendicular magnetic recording medium according to claim 8 , wherein
the non-magnetic substance includes any of chrome, oxygen, or an oxide, or a plurality thereof.
10. The perpendicular magnetic recording medium according to claim 9 , wherein
the oxide includes one or a plurality of oxides selected from the group of SiO 2 , TiO 2 , Cr 2 O 3 , Ta 2 O 5 , Nb 2 O 5 , B 2 O 3 , and ZrO 2 .
11. The perpendicular magnetic recording medium according to claim 9 , wherein
an oxide included in the second magnetic recording layer includes one or a plurality of oxides selected from the group of SiO 2 , TiO 2 , Cr 2 O 3 , Ta 2 O 5 , Nb 2 O 5 , B 2 O 3 , and ZrO 2 .
12. The perpendicular magnetic recording medium according to claim 1 , wherein
the non-magnetic substance includes any of chrome, oxygen, or an oxide, or a plurality thereof.
13. The perpendicular magnetic recording medium according to claim 12 , wherein
the oxide includes one or a plurality of oxides selected from the group of SiO 2 , TiO 2 , Cr 2 O 3 , Ta 2 O 5 , Nb 2 O 5 , B 2 O 3 , and ZrO 2 .
14. The perpendicular magnetic recording medium according to claim 12 , wherein
an oxide included in the second magnetic recording layer includes one or a plurality of oxides selected from the group of SiO 2 , TiO 2 , Cr 2 O 3 , Ta 2 O 5 , Nb 2 O 5 , B 2 O 3 , and ZrO 2 .
15. A perpendicular magnetic recording medium comprising:
a base,
at least a ground layer,
a first magnetic recording layer,
a second magnetic recording layer, and
at least a third magnetic recording layer, said layers being provided in this order on the base, wherein
the first magnetic recording layer, the second magnetic recording layer and the at least a third magnetic recording layer are ferromagnetic layers of a granular structure in which grain boundary parts made of a non-magnetic substance are each formed between crystal grains each grown in a columnar shape,
A<B when an average particle diameter of the crystal grains in the first magnetic recording layer is taken as A nm and an average particle diameter of the crystal grains in the second magnetic recording layer is taken as B nm, and
the average particle diameter of the magnetic particles of an upper magnetic recording layer selected from the second and third magnetic layers, relative to the base side is larger than the average particle diameter of the magnetic particles of a lower magnetic recording layer selected from the first and second magnetic layers, relative to the upper magnetic recording layer, and
further comprising a non-magnetic granular layer between the ground layer and the first magnetic recording layer, the non-magnetic granular layer having an average particle diameter smaller than the average particle diameter of the first magnetic recording layer.
16. The perpendicular magnetic recording medium according to claim 15 wherein the non-magnetic granular layer includes non-magnetic crystal grains made of a Co alloy and a grain boundary part that comprises at least one of SiOx, Cr, CrO 2 , TiO 2 , ZrO 2 and Ta 2 O 5 .
17. The perpendicular magnetic recording medium according to claim 16 wherein the non-magnetic granular layer comprises Co, Cr, SiO 2 and at least one of Ru, Rh, Pd, Ag, Os, Ir and Au.