Perpendicular magnetic recording media and magnetic storage apparatus using the same
View Patent ↗Embodiments of the present invention provide a perpendicular magnetic recording media having excellent resolution, signal to noise ratio (S/N), and a small adjacent track erasure. According to one embodiment, underlayers for controlling the orientation and segregation of a magnetic layer, a magnetic layer including an oxide and an alloy of magnetic materials mainly composed of Co, Cr, and Pt, and a ferromagnetic-metal layer which does not contain oxygen, are formed over a substrate. The magnetic layer has at least two layers including ferromagnetic grains and oxides, a first magnetic layer, which is the part of the magnetic layer closer to the substrate, has grain boundaries mainly composed of Cr oxide and at least one oxide selected from Si, Ti, Nb, and Ta, and grain boundaries of a second magnetic layer at the ferromagnetic-metal layer side includes at least one oxide selected from Si, Ti, Nb, and Ta in which Cr oxide is less than the first magnetic layer.
1. A perpendicular magnetic recording medium comprising:
an underlayer provided over a substrate;
a magnetic layer formed over said underlayer, in which magnetic grains comprising Co, Cr, and Pt with columnar structure and oxides are contained; and
a ferromagnetic-metal layer which is formed over said magnetic layer and which does not contain an oxide,
wherein said magnetic layer comprises at least two layers including a first magnetic layer formed at an underlayer side of the magnetic layer and a second magnetic layer formed at a ferromagnetic-metal layer side of the magnetic layer, in which grain boundaries of said first magnetic layer include a Cr oxide and at least one oxide selected from Si, Ti, Nb, and Ta, and grain boundaries of said second magnetic layer include at least one oxide selected from Si, Ti, Nb, and Ta where the sum of element concentrations of Cr and oxygen in any Cr oxide in the second magnetic layer is smaller than that in said first magnetic layer and is greater than 0 at % and less than 5 at %.
2. The perpendicular magnetic recording medium according to claim 1 , wherein
the grain boundary width of said second magnetic layer is narrower than the grain boundary width of said first magnetic layer, wherein a thickness of the ferromagnetic-metal layer is between about 1 nm and about 5 nm.
3. The perpendicular magnetic recording medium according to claim 1 , wherein
crystal grains of said ferromagnetic-metal layer and crystal grains of said second magnetic layer exist with a correspondence of 1 to many or many to 1, and crystal grains of said ferromagnetic-metal layer have a structure continuously grown over grain boundaries of said second magnetic layer.
4. The perpendicular magnetic recording medium according to claim 1 , wherein
crystal grains of said ferromagnetic-metal layer are smaller than crystal grains of said second magnetic layer.
5. The perpendicular magnetic recording medium according to claim 1 , wherein
the sum of concentrations of Cr element and oxygen element in the Cr oxide of the second magnetic layer is 4.3 at. % or less in the region of film thickness of about 2 nm from the ferromagnetic-metal layer side of the magnetic layer.
6. The perpendicular magnetic recording medium according to claim 1 , wherein
the sum of concentrations of Cr element and oxygen element contained in the Cr oxide is 7 at. % or more and 20 at. % or less in the region of film thickness of about 4 nm from the substrate side of the magnetic layer.
7. The perpendicular magnetic recording medium according to claim 1 , wherein
the total amount of each element contained in the oxide of said second magnetic layer is 3.6 at. % or more and 13 at. % or less.
8. The perpendicular magnetic recording medium according to claim 1 , wherein
the total amount of each element contained in the oxide of said first magnetic layer is 15 at. % or more and 30 at. % or less.
9. The perpendicular magnetic recording medium according to claim 1 ,
wherein
a CoRu alloy layer, a CoCr alloy layer, or a layer which has a granular structure of CoCr and Si0 2 is provided between said second magnetic layer and said ferromagnetic-metal layer.
10. A perpendicular magnetic recording medium comprising:
an underlayer provided over a substrate;
a magnetic layer formed over said underlayer, in which magnetic grains comprising Co, Cr, and Pt with columnar structure and oxides are contained;
a ferromagnetic-metal layer which is formed over said magnetic layer and which does not contain an oxide,
wherein said magnetic layer comprises a Cr oxide in grain boundaries thereof, wherein the Cr oxide has a concentration gradient that varies in a film thickness direction of the magnetic layer from an underlayer side of the magnetic layer towards a ferromagnetic-metal layer side of the magnetic layer, wherein the magnetic layer includes the Cr oxide and at least one oxide selected from Si, Ti, Nb, and Ta, where the sum of element concentrations of Cr and oxygen contained in the Cr oxide decreases from the underlayer side to the ferromagnetic-metal layer side to less than 5 at. %, wherein the magnetic layer has no clear separate layer structure.
11. The perpendicular magnetic recording medium according to claim 10 , wherein
the grain boundary width of said magnetic layer at said ferromagnetic-metal layer side is narrower than the grain boundary width from the interface at said underlayer side.
12. The perpendicular magnetic recording medium according to claim 10 , wherein
crystal grains of said ferromagnetic-metal layer and crystal grains of said magnetic layer exist with a correspondence of 1 to many or many to 1, and crystal grains of said ferromagnetic-metal layer have a structure continuously grown over grain boundaries of said magnetic layer.
13. The perpendicular magnetic recording medium according to claim 10 , wherein
crystal grains of said ferromagnetic-metal layer are smaller than crystal grains of said magnetic layer.
14. The perpendicular magnetic recording medium according to claim 10 , wherein
the sum of the concentrations of Cr element and oxygen element contained in the Cr oxide is 4.3 at. % or less in the region of film thickness of about 2 nm from the ferromagnetic-metal layer side.
15. The perpendicular magnetic recording medium according to claim 10 , wherein
the sum of the concentrations of Cr element and oxygen element contained in the Cr oxide is 7 at. % or more and 20 at. % or less in the region of film thickness of about 4 nm from the underlayer side.
16. The perpendicular magnetic recording medium according to claim 10 , wherein
the total amount of each element contained in the oxide in the region of said magnetic layer at said ferromagnetic metallic side is 3.6 at. % or more and 13 at. % or less.
17. The perpendicular magnetic recording medium according to claim 10 , wherein
the total amount of each element contained in the oxide in the region of said magnetic layer at said underlayer side is 15 al. % or more and 30 al. % or less.
18. The perpendicular magnetic recording medium according to claim 10 , wherein
a CoRu alloy layer, a CoCr alloy layer, or a layer having a granular structure of CoCr and Si02 is provided between said magnetic layer and said ferromagnetic-metal layer.
19. A magnetic storage apparatus comprising:
perpendicular magnetic recording media comprising;
an underlayer provided over a substrate;
a magnetic layer formed over said underlayer, in which magnetic grains comprising Co, Cr, and Pt with columnar structure and oxides are contained; and
a ferromagnetic-metal layer which is formed over said magnetic layer and which does not contain an oxide,
wherein said magnetic layer comprises at least two layers including a first magnetic layer formed at said underlayer side and a second magnetic layer formed at said ferromagnetic-metal layer side, in which grain boundaries of said first magnetic layer include a Cr oxide and at least one oxide selected from Si, Ti, Nb, and Ta, and grain boundaries of said second magnetic layer include at least one oxide selected from Si, Ti, Nb, and Ta where the sum of element concentrations of Cr and oxygen contained in the Cr oxide is smaller than that in said first magnetic layer and is greater than 0 at % and less than 5 at. %, wherein crystal grains of said ferromagnetic-metal layer and crystal grains of said magnetic layer exist with a correspondence of 1 to many or many to 1, and crystal grains of said ferromagnetic-metal layer have a structure continuously grown over grain boundaries of said magnetic layer;
a unit for driving said perpendicular magnetic recording medium in the recording direction;
a magnetic head having a write head and read head;
a unit for driving said magnetic head relative to said perpendicular magnetic recording medium; and
a signal processing unit for processing input signals and output signals to said magnetic head.