Coating processes – Magnetic base or coating – Magnetic coating
Reexamination Certificate
2002-09-18
2004-11-30
Rickman, Holly (Department: 1773)
Coating processes
Magnetic base or coating
Magnetic coating
C427S128000, C427S130000
Reexamination Certificate
active
06824817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of making a magnetic multilayer film of FePt having an L1
0
ordered structure, a method of making a magnetic recording medium, a magnetic multilayer film, and a magnetic recording medium.
2. Related Background Art
A magnetic multilayer film of FePt in which Fe and Pt monatomic layers are alternatively laminated has been known, for example, as disclosed in Japanese Patent Application Laid-Open No. HEI 8-186022. This magnetic multilayer film has an L1
0
ordered structure, thus yielding a high magnetic anisotropy energy constant, and is expected to be applied to high-density recording media, bias magnets of monolithic microwave integrated-circuits, and the like.
SUMMARY OF THE INVENTION
For improving performances of such a magnetic multilayer film and a magnetic recording medium utilizing the same, making methods which can restrain the magnetic multilayer film from being damaged have been in demand.
It is an object of the present invention to provide a method of making a magnetic multilayer film, a method of making a magnetic recording medium, a magnetic multilayer film, and a magnetic recording medium which can suppress damages.
The inventors conducted diligent studies and, as a result, have found a method of making a magnetic multilayer film which can suppress damages, by taking account of the substrate temperature at the time of laminating monatomic layers.
The present invention provides a method of making a magnetic multilayer film, comprising a monatomic layer laminating step of alternately laminating Fe and Pt monatomic layers on a substrate having a temperature of 120 to 240° C.
The magnetic multilayer film obtained by the method of making a magnetic multilayer film in accordance with the present invention has an L1
0
ordered structure so as to exhibit a high magnetic anisotropy energy constant, a (001) surface parallel to the substrate surface, and a high perpendicular magnetic anisotropy, while its coercive force in a direction perpendicular to the substrate surface and the squareness ratio of its magnetization curve in a direction perpendicular to the substrate surface are large, so that it is usable as a magnetic recording film for a magnetic recording medium and the like. Also, since the magnetic multilayer film is formed while the substrate temperature is 120 to 240° C., the temperature load on the substrate or the like is lowered as compared with conventional making methods in which the substrate temperature is about 500° C., whereby damages to the magnetic multilayer film are reduced.
Preferably, the monatomic layer laminating step is carried out at a pressure of 1×10
−6
Pa or less. Laminating monatomic layers under such an ultrahigh vacuum improves the purity of magnetic multilayer films and restrains the films from oxidizing and so forth.
Preferably, the method further comprises a buffer layer forming step of forming a buffer layer on the substrate prior to the monatomic layer laminating step.
Forming a buffer layer improves the wettability and flatness of the substrate, whereby the regularity of the L1
0
structure in the magnetic multilayer film becomes higher, which improves performances of the magnetic multilayer film.
Preferably, the buffer layer is formed from Pt, Au, or Ag and has a thickness of about 10 to 50 nm, whereby the buffer layer fully exhibits its functions.
Preferably, the method further comprises a seed layer forming step of forming a seed layer on the substrate prior to the buffer layer forming step.
When the seed layer is formed, the buffer layer laminated thereon can attain a (001) surface orientation, so that the orientation of the (001) surface of the magnetic multilayer film can be made parallel to the substrate surface more reliably, whereby a magnetic multilayer film having a high perpendicular magnetic anisotropy can be formed favorably.
Preferably, the seed layer is formed from Fe, Au, Ag, Ni, or Co and has a thickness of 0.2 to 2 nm, whereby the seed layer fully exhibits its functions.
The present invention provides a method of making a magnetic recording medium, including the above-mentioned method of making a magnetic multilayer film.
Since the method of making a magnetic recording medium in accordance with the present invention includes the above-mentioned method of making a magnetic multilayer film, a magnetic multilayer film having high magnetic performances can be obtained while its damages are reduced, whereby the magnetic recording medium attains a higher reliability.
The present invention provides a magnetic multilayer film comprising a substrate, seed and buffer layers successively laminated thereon, and Fe and Pt monatomic layers alternately laminated on the buffer layer.
In the magnetic multilayer film in accordance with the present invention, the seed layer makes the buffer layer reliably attain a (001) surface orientation, so that the (001) surface of the magnetic multilayer film laminated on the buffer layer can achieve an orientation parallel to the substrate surface more securely, whereby the perpendicular magnetic anisotropy becomes higher, while the coercive force in a direction perpendicular to the substrate surface and the squareness ratio of the magnetization curve in a direction perpendicular to the substrate surface become greater.
Preferably, the seed layer has a thickness of 0.2 to 2 nm and is formed from Fe, Au, Ag, Ni, or Co, whereas the buffer layer has a thickness of 10 to 50 nm and is formed from Pt, Au, or Ag. As a consequence, the seed and buffer layers fully exhibit their functions.
The present invention provides a magnetic recording medium comprising the above-mentioned magnetic multilayer film as a magnetic recording film. It yields a magnetic recording medium having a high perpendicular magnetic anisotropy, a large coercive force in a direction perpendicular to the substrate surface, and a great squareness ratio of the magnetization curve in a direction perpendicular to the substrate surface as mentioned above, since it has seed and buffer layers.
REFERENCES:
patent: 6086974 (2000-07-01), Thiele et al.
patent: 6605321 (2003-08-01), Ravelosona-Ramasitera et al.
patent: A 8-186022 (1996-07-01), None
Shima et al., “Synthesis ordered Fe/Pt alloys at low temperature by alternate monoatomic layer deposition”, Outline of Lecture to the Japan Institute of Metals Annual Meeting, 2001 w/abstract.
Shima et al., “Low-temperature fabrication of L10ordered FePt alloy by alternate monatomic layer deposition”, Applied Physics Letters, vol. 80, No. 2, pp. 288-290, 2002.
Araki Satoru
Mitani Seiji
Moriguchi Takuto
Shima Toshiyuki
Takanashi Koki
Rickman Holly
TDK Corporation
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