Magnetic thin film and method for forming the film, and magnetic thin film-applied device
View Patent ↗Disclosed are a magnetic thin film capable of providing a high uniaxial magnetic anisotropy, Ku, while suppressing the saturation magnetization Ms thereof, and a method for forming the film; and also disclosed are various devices to which the magnetic thin film is applied. The magnetic thin film comprises a Co-M-Pt alloy having an L11-type ordered structure (wherein M represents one or more metal elements except Co and Pt). For example, the Co-M-Pt alloy is a Co—Ni—Pt alloy of which the composition comprises from 10 to 35 at. % of Co, from 20 to 55 at. % of Ni and a balance of Pt. The magnetic thin film is applicable to perpendicular magnetic recording media, tunnel magneto-resistance (TMR) devices, magnetoresistive random access memories (MRAM), microelectromechanical system (MEMS) devices, etc.
1. A magnetic thin film comprising a Co-M-Pt alloy having an L11-type ordered structure, wherein the Co-M-Pt alloy is one of the following:
a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt, or
a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt.
2. The magnetic thin film according to claim 1 , wherein the magnetization easy axis of the film is oriented perpendicularly to the film surface.
3. The magnetic thin film according to claim 1 , wherein the Co-M-Pt alloy is either a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt.
4. The magnetic thin film according to claim 1 , wherein the Co-M-Pt alloy is a Co—Ni—Pt alloy comprising from 10 to 35 at. % of Co, from 20 to 55 at. % of Ni and a balance of Pt.
5. The magnetic thin film according to claim 1 , wherein the Co-M-Pt alloy is either a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt.
6. A method for forming a magnetic thin film of claim 1 on a substrate using a high-vacuum magnetron sputtering method, wherein the substrate temperature is within a range of from 150° C. to 500° C. and the degree of vacuum before film formation is at most 1×10 −4 Pa.
7. The method for forming a magnetic thin film according to claim 6 , wherein the substrate temperature is from 270° C. to 400° C.
8. The method for forming a magnetic thin film according to claim 7 , wherein the degree of vacuum is at most 7×10 −7 Pa.
9. A magnetic thin film according to claim 1 , where said film has a granular structure that comprises
(i) ferromagnetic crystal grains of mainly a Co-M-Pt alloy having an L 11 -type ordered structure, wherein the Co-M-Pt alloy is one of the following:
a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt, or
a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt
and
(ii) a non-magnetic grain boundary surrounding the ferromagnetic crystal grains.
10. The magnetic thin film according to claim 9 , wherein the magnetization easy axis of the film is oriented perpendicularly to the film surface.
11. The magnetic thin film according to claim 9 , wherein the Co-M-Pt alloy is either a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt.
12. The magnetic thin film according to claim 9 , wherein the Co-M-Pt alloy is a Co—Ni—Pt alloy comprising from 10 to 35 at. % of Co, from 20 to 55 at. % of Ni and a balance of Pt.
13. The magnetic thin film according to claim 9 , wherein the Co-M-Pt alloy is either a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt.
14. A method for forming a magnetic thin film of claim 9 on a substrate using a high-vacuum magnetron sputtering method, wherein the substrate temperature is within a range of from 150° C. to 500° C. and the degree of vacuum before film formation is at most 1×10 −4 Pa.
15. A perpendicular magnetic recording medium comprising:
a substrate, and
at least a magnetic layer formed on said substrate,
wherein the magnetic layer is a magnetic thin film comprising a Co-M-Pt alloy having an L11-type ordered structure, wherein the Co-M-Pt alloy is one of the following:
a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt, or
a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt.
16. A perpendicular magnetic recording medium according to claim 15 , wherein said magnetic thin film has a granular structure that comprises (i) ferromagnetic crystal grains of mainly a Co-M-Pt alloy having an L11-type ordered structure, wherein M represents one or more metal elements excluding Co and Pt, the Co-M-Pt alloy is one of the following:
a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt, or
a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt
and
(ii) a non-magnetic grain boundary surrounding the ferromagnetic crystal grains.
17. A tunnel magneto-resistance (TMR) device comprising a magnetic thin film which comprises a Co-M-Pt alloy having an L11-type ordered structure, wherein the Co-M-Pt alloy is one of the following:
a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt, or
a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt.
18. A magnetoresistive random access memory (MRAM) comprising a magnetic thin film which comprises a Co-M-Pt alloy having an L11-type ordered structure, wherein the Co-M-Pt alloy is one of the following:
a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt, or
a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt.
19. An MEMS device comprising a magnetic thin film which comprises a Co-M-Pt alloy having an L11-type ordered structure, wherein the Co-M-Pt alloy is one of the following:
a Co—Ni—Pt alloy or a Co—Ni-M2-Pt alloy in which M2 represents one or more metal elements excluding Co, Ni and Pt, or
a Co—Fe—Pt alloy or a Co—Fe-M3-Pt alloy in which M3 represents one or more metal elements excluding Co, Fe and Pt.