JP3559333B2 - Magnetic multilayer film, method of manufacturing the same, and magneto-optical recording medium - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a magnetic multilayer film exhibiting magneto-optical Kerr rotation, a method of manufacturing the same, and a magneto-optical recording medium having the magnetic multilayer film as a magneto-optical recording film.
[0002]
[Prior art]
Today's thin film fabrication technology, in which dissimilar metals can be alternately laminated at the atomic layer level, enables the production of multilayer films having a regular laminated structure that does not exist in nature, that is, metal artificial lattices.
[0003]
Mat. Res. Soc. Symp. Proc. , 151, 123 (1989) (hereinafter referred to as Reference 1), when [Fe (4A) / Au (28A)] ₁₀ is used in an Fe / Au artificial lattice film with an Fe (110) orientation, an effective perpendicular magnetic field is obtained. It is reported that the anisotropic energy constant is 1.3 × 10 ⁶ erg / cm ³ .
[0004]
In the Journal of the Japan Society of Applied Magnetics, 14, 343 (1990) (hereinafter referred to as Reference 2), an artificial lattice film of Fe (001) / Au (001) orientation [Fe (1.5 A) / Au (29A) )] it has been reported that was prepared _20. The effective perpendicular magnetic anisotropy energy constant of this artificial lattice film is 2.5 × 10 ⁶ erg / cm ³ . In Reference 2, the effective perpendicular magnetic anisotropy energy constant is represented by K⊥, and FIG. 5, when t _Fe = 2.0 A, t _Fe K⊥ = 0.05 erg / cm ² . Therefore, K⊥ = 0.05 / (2 × 10 ⁻⁸ ) = 2.5 × 10 ⁶ erg / cm ³ .
[0005]
However, in the artificial lattice films described in References 1 and 2, respectively, a satisfactory perpendicular magnetization film cannot be obtained because the perpendicular magnetic anisotropy is not large, and the magneto-optical recording of the perpendicular magnetic recording film and the magneto-optical recording medium is not performed. It is difficult to put it to practical use as a membrane. Further, in the above-described conventional Fe / Au multilayer film, the Au layer thickness was as large as 28 A or more, and the perpendicular magnetization film was not formed unless the layer thickness ratio Fe / Au was 1/7 or less. For this reason, the Kerr rotation angle becomes small, which is not suitable for a magneto-optical recording film.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a magnetic multilayer film having a large perpendicular magnetic anisotropy and a large Kerr rotation angle, and a magneto-optical recording medium using this magnetic multilayer film as a magneto-optical recording film.
[0007]
[Means for Solving the Problems]
Such an object is achieved by any one of the following constitutions (1) to (5).
(1) a magnetic multilayer film formed on a substrate via a seed layer of Fe or Cr having a thickness of 5 to 20 A and a buffer layer of Au, Pt or Ag having a thickness of 150 to 3000 A ;
A magnetic multilayer film in which a single atomic layer of Fe and a single atomic layer of Au are stacked one by one and have a (001) plane orientation.
(2) The magnetic multilayer film according to the above (1), wherein only a peak showing (001) plane orientation is recognized in the X-ray diffraction chart.
(3) A seed layer made of Fe or Cr and having a thickness of 5 to 20 A and a buffer layer made of Au, Pt or Ag having a thickness of 150 to 3000 A are sequentially formed on a substrate, and then a single atom of Fe is formed by vapor deposition. A method for manufacturing a magnetic multilayer film in which layers and Au monoatomic layers are alternately stacked to form an ordered alloy film.
(4) The method for manufacturing a magnetic multilayer film according to (3), wherein the magnetic multilayer film according to (1) or (2) is formed.
(5) A magneto-optical recording medium having the magnetic multilayer film of (1) or (2) as a magneto-optical recording film.
[0008]
[Action and effect]
In the present invention, unlike a conventionally known mere artificial lattice film, a monolayer of Fe and a monolayer of Au are alternately stacked one by one, and the magnetic property is equivalent to an ordered alloy having a (001) plane orientation. Obtain an artificial lattice multilayer film. Such an Fe / Au multilayer film equivalent to an ordered alloy was first realized by the present invention. This magnetic multilayer film is preferably formed by an ultra-high vacuum deposition method.
[0009]
The multilayer film thus manufactured has a large perpendicular magnetic anisotropy constant and therefore is a good perpendicular magnetization film, and has a large Kerr rotation angle, and is useful as a perpendicular magnetic recording film and a magneto-optical recording film.
[0010]
The artificial lattice films described in Documents 1 and 2 are different from the magnetic multilayer film of the present invention because they are not formed by stacking a monolayer of Fe and a monolayer of Au.
[0011]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples of the present invention.
[0012]
The ultimate vacuum degree was set to 3 × 10 ⁻¹⁰ Torr, and a 10 A-thick Fe (001) seed layer was formed on a MgO (001) substrate under a pressure of less than 2 × 10 ⁻⁹ Torr by a vapor deposition method. A 500 A thick Au (001) buffer layer was formed by evaporation and then annealed at 500 ° C. The substrate temperature (Ts) at the time of forming each layer was 200 ° C. As the substrate, GaAs (001), Si (001), or the like may be used in addition to MgO (001). As the buffer layer, Pt (001), Ag (001), or the like may be used in addition to Au (001). It is preferable that the thickness of the buffer layer be about 150 to 3000 A. The seed layer provided between the buffer layer and the substrate is for promoting crystal growth. In particular, when an Au layer is used as the buffer layer, it is preferable to provide this seed layer. The thickness of the seed layer is preferably about 5 to 20A. The seed layer is not limited to Fe but may be Cr or the like. The temperature at the time of forming the seed layer and the buffer layer on the substrate is preferably from room temperature to about 500 ° C.
[0013]
Next, a [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film was formed on the buffer layer under the above pressure. The substrate temperature was 70 ° C. A vapor deposition apparatus having two independent electron guns was used. 1 ML means a monoatomic layer. The thickness of Fe (1ML) is 1.4 A, the thickness of Au (1ML) is 2.0 A, and this multilayer film is obtained by stacking 100 units of Fe (1ML) + Au (1ML) as one unit. It is. The deposition rate was 0.1 A / min. During the vapor deposition, a RHEED (Reflection High Energy Electron Diffraction) pattern was monitored, and it was confirmed that the (001) oriented monoatomic layers were epitaxially grown one by one.
[0014]
Usually, the substrate temperature during the formation of the multilayer film is preferably from room temperature to 300 ° C. Further, the number of lamination units when Fe (1 ML) + Au (1 ML) is one unit is not particularly limited, but is usually preferably about 10 to 300. The pressure at the time of forming the multilayer film is preferably 1 × 10 ⁻⁸ Torr or less, and more preferably about 1 × 10 ^{−10 to} 3 × 10 ⁻⁹ Torr.
[0015]
The RHEED patterns shown in FIGS. 1 to 4 are those in which FIG. 1 shows an Au buffer layer, FIG. 2 shows an Fe layer as a first layer, FIG. 3 shows an Au layer as a second layer, and FIG. 4 shows an Au layer as an uppermost layer. It is. These are all Au [110] incident. From the striped pattern in each figure, it can be seen that the surface of each film is fairly flat on the atomic scale, and that a film is formed by epitaxially growing one monolayer of Fe and one monolayer of Au. FIG. 5 shows an X-ray diffraction chart of this multilayer film. In FIG. 5, some peaks are shown enlarged. In the X-ray diffraction chart, a peak indicating (001) plane orientation is observed, and no peak indicating another orientation is observed. This indicates that a film having a regular structure at the atomic level was formed.
[0016]
The magnetic anisotropy of this multilayer film was measured at room temperature with a SQUID magnetometer. FIG. 6 shows the magnetization curves of this multilayer film in the directions parallel (H //) and perpendicular (H⊥) to the film surface. From this magnetization curve, it can be seen that this multilayer film has a large perpendicular magnetic anisotropy.
[0017]
The magneto-optical Kerr rotation angle (θ _k ) of this multilayer film at a wavelength (λ) of 633 nm was measured at room temperature. FIG. 7 shows a Kerr loop showing the relationship between the magnetic field strength and the Kerr rotation angle. As shown in the figure, the saturation Kerr rotation angle at 633 nm of this multilayer film was 0.25 degrees.
[0018]
The effective perpendicular magnetic anisotropy constant of this multilayer film was 8.5 × 10 ⁶ erg / cm ³ . This value is to be compared with the effective perpendicular magnetic anisotropy energy constant of the above-mentioned documents 1 and 2. Therefore, it can be seen that the present invention provides a better perpendicular magnetic anisotropy than the artificial lattice films described in the above-mentioned References 1 and 2. In this multilayer film, the essential perpendicular magnetic anisotropy constant obtained by adding the shape anisotropy 2πMs ² to the effective perpendicular magnetic anisotropy constant was 1.1 × 10 ⁷ erg / cm ³ . . The saturation magnetization Ms was 650 emu / cc.
[Brief description of the drawings]
FIG. 1 is a drawing substitute photograph showing a crystal structure, and is a RHEED pattern of an Au buffer layer provided as a base of a [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film.
FIG. 2 is a drawing substitute photograph showing a crystal structure, and is a RHEED pattern of an Fe layer which is a first layer of a [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film.
FIG. 3 is a drawing substitute photograph showing a crystal structure, and is a RHEED pattern of an Au layer which is a second layer of the [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film.
FIG. 4 is a drawing substitute photograph showing a crystal structure, and is a RHEED pattern of an Au layer which is the uppermost eyebrow of a [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film.
FIG. 5 is an X-ray diffraction chart of a [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film.
FIG. 6 is a magnetization loop of a [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film.
FIG. 7 is a Kerr loop of [Fe (1ML) / Au (1ML)] ₁₀₀ multilayer film.

Claims (5)

A magnetic multilayer film formed on a substrate via a 5 to 20 A thick seed layer made of Fe or Cr and a 150 to 3000 A thick buffer layer made of Au, Pt, or Ag ;
A magnetic multilayer film in which a single atomic layer of Fe and a single atomic layer of Au are stacked one by one and have a (001) plane orientation. 2. The magnetic multilayer film according to claim 1, wherein in the X-ray diffraction chart, only a peak indicating (001) plane orientation is recognized. A 5 to 20 A thick seed layer made of Fe or Cr and a 150 to 3000 A thick buffer layer made of Au, Pt, or Ag are sequentially formed on a substrate, and then a Fe monoatomic layer and Au are formed by vapor deposition. A method of manufacturing a magnetic multilayer film in which ordered alloy films are formed by alternately stacking monoatomic layers. The method for manufacturing a magnetic multilayer film according to claim 3, wherein the magnetic multilayer film according to claim 1 or 2 is formed. A magneto-optical recording medium comprising the magnetic multilayer film according to claim 1 as a magneto-optical recording film.

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