JPH0354443B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a garnet thin film element suitable for use as a magnetic memory or a magneto-optical memory, and a method for manufacturing the same.

In recent years, rare earth iron garnet R ₃ (Fe, M) ₅ O ₁₂
(R: rare earth element, M: Al ³⁺ , Ga ³⁺ , Sc ³⁺ ,
Iron garnet R _3-x Bi _x (Fe,M) ₅ O ₁₂ , in which a part of R in Tl ³⁺ , (Co ²⁺ +Ti ⁴⁺ ), etc., is replaced with Bi, is attracting attention. This Bi-substituted rare earth iron garnet is
By replacing a part of R with Bi, it has the property that the Faraday rotation angle θ _F can be increased without increasing the absorption coefficient α too much,
It is generally excellent as a photothermal magnetic recording material.

In order to improve the performance of Bi-substituted rare earth iron garnets having these properties as photothermal magnetic recording materials, it is possible to increase the Bi substitution amount x and the Faraday rotation angle θ _F , but conventional liquid phase epitaxy It has been difficult to produce a Bi-substituted rare earth iron garnet thin film with a large Bi substitution amount x using production methods such as the Yall method.

The present inventors, in Japanese Patent Application No. 58-216750,
A method for manufacturing a magnetic thin film in which a high concentration Bi-substituted rare earth iron garnet single crystal thin film in which Bi is dissolved in solid solution up to the solid solution limit (50% of dodecahedral positions) can be epitaxially grown on a GGG substrate by sputtering method. proposed. However, this manufacturing method has the disadvantage that the substrates that can be used are limited to GGG substrates, so it is difficult to form a high concentration Bi-substituted rare earth iron garnet thin film on an amorphous substrate such as a glass substrate. A manufacturing method that would allow for this was desired.

Such requirements have existed for rare earth iron garnet thin films other than those mentioned above, and various attempts have been made. However, the thin films obtained to date are polycrystalline in-plane magnetized films with magnetization in a direction parallel to the plane, and a perpendicularly magnetized film preferable as a magnetic recording and photothermal magnetic recording material has not yet been obtained. . Furthermore, at present, no attempt has been made to form a Bi-substituted rare earth iron garnet perpendicularly magnetized film on an amorphous substrate.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a garnet thin film element composed of a garnet thin film having extremely good perpendicular magnetization characteristics, and a method for manufacturing the same.

That is, the garnet thin film element according to the present invention has a (111) orientation Ba _1-xy provided on a predetermined substrate.
Sr _x Ca _y F ₂ film (0≦x+y<1) and this
and a garnet thin film provided on the Ba _1-xy Sr _x Ca _y F ₂ film. With this configuration, the perpendicular magnetization characteristics can be made extremely good.

Further, the method for manufacturing a garnet thin film element according to the present invention involves growing a Ba _1-xy Sr _x Ca _y F ₂ film (where 0≦x+y<1) in the (111) plane orientation on a predetermined substrate, and then A garnet thin film is grown azimuthally on the Ba _1-xy Sr _x Ca _y F ₂ film. By doing so, a garnet thin film element with extremely good perpendicular magnetization characteristics can be manufactured.
Furthermore, since the material of the substrate can be selected from various types, it is extremely convenient in terms of manufacturing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a garnet thin film element and a method for manufacturing the same according to the present invention will be described below with reference to the drawings. In this example, Bi expressed as (Y, Bi) ₃ (Fe, Al) ₅ O ₁₂ was used as the garnet thin film.
Using substituted rare earth iron garnet thin film, Ba _1-xy Sr _x
A BaF ₂ film was used as the Ca _y F ₂ film, and a quartz glass substrate was used as the substrate. Naoko (Y, Bi) ₃
(Fe, Al) ₅ O ₁₂ is yttrium iron garnet
In Y ₃ Fe ₅ O ₁₂ (YIG), part of Y is replaced with Bi and part of Fe is replaced with Al,
The former increases the Faraday rotation angle θ _F without significantly increasing the absorption coefficient α, while the latter decreases the absorption coefficient α and lowers the saturation magnetization, making it easier to obtain a perpendicularly magnetized film and also lowering the Curie temperature. Are known.

First, as shown in FIG. 1A, a quartz glass substrate 2 is placed on a sample stage 1 of a vacuum evaporation apparatus, and BaF ₂ 4 as an evaporation substance is inserted into a hollow portion of a filament 3 constituting a heating source. Next, after evacuating the inside of the vacuum evaporation apparatus to a predetermined vacuum level, for example, about 10 ^-4 Pa, the filament 3
BaF ₂ 4 is heated to a predetermined temperature. This results in
Atoms and molecules of Ba, F, and BaF ₂ constituting BaF ₂ 4 are evaporated, and a quartz glass substrate 2 is heated to, for example, 650° C. by a heater 5 via a sample stage 1.
(111) on this quartz glass substrate 2.
A polycrystalline BaF ₂ film 6 in which planes are dominantly grown is formed. Note that the thickness of the BaF ₂ film 6 was set to 0.4 μm in this example.

Next, as shown in FIG. 1B, the quartz glass substrate 2 on which the BaF ₂ film 6 described above is formed is placed on the stainless steel electrode plate (sample stage) 7 of the radio frequency (RF) sputtering device. , a target 9 is attached to the electrode plate 8. Furthermore, this target 9
consists of a disc-shaped sintered body of polycrystalline iron garnet represented by the composition formula Bi _2.0 Y _1.0 Fe _3.8 Al _1.2 O ₁₂ .

Next, after evacuating the inside of the sputtering device to a predetermined degree of vacuum, Ar and O ₂ are added to the sputtering device.
A mixed gas (Ar:O ₂ =9:1) is introduced up to about 7Pa. With the degree of vacuum stable, the electrode plate 7
A predetermined high frequency voltage is applied between the electrode plate 8 and the electrode plate 8 to start glow discharge. Ar ⁺ generated by this discharge
The ions sputter on the surface of the target 9, and the sputtering removes Bi, Y,
Atoms such as Fe, Al, and O are released. These detached atoms adhere to the BaF ₂ film 6 heated to, for example, 450° C. by the heater 10 via the _electrode plate 7, and (Y, Bi) ₃ (Fe, Al _{） 5O12}
A thin film (hereinafter referred to as thin film) 11 is formed, and a garnet thin film element consisting of the quartz glass substrate 2, the BaF ₂ film 6 and the thin film 11 is completed. Note that when the power used for sputtering was 110 W and the sputtering time was 2 hours and 30 minutes, the thickness of the obtained thin film 11 was 0.8 μm.

When the crystallinity of the thin film 11 produced in the above example was examined by X-ray diffraction, it was found that it was a polycrystal in which the (111) plane grew predominantly parallel to the film surface (that is, oriented growth). did. As a result of observation using an optical microscope, the thin film 11 has an arabesque-like and bubble-like magnetic domain structure, and measurements have revealed that it is an extremely good perpendicularly magnetized film with the following excellent characteristics. was made into

That is, as shown in FIG. 2, the Faraday rotation angle θ _F of the thin film 11 with respect to the magnetic field H in the direction perpendicular to the film surface
When the hysteresis characteristics of the film were measured, a loop with good squareness was obtained, and magnetic torque measurements revealed that it was a perpendicularly magnetized film. Further, the Faraday rotation angle θ _F is extremely large at about 1.5°, and the coercive force H _c is also sufficiently large at about 200 Oe. In this way, the thin film 11
It can be seen that the garnet thin film element has extremely favorable properties as a magnetic recording material, and therefore the garnet thin film element has extremely good properties. Furthermore, since a perpendicularly magnetized film having excellent properties as shown in FIG. 2 is obtained, it is assumed that Bi, which imparts larger perpendicular magnetic anisotropy, is dissolved in solid solution in the thin film 11 up to the solid solution limit. is estimated. In Fig. 2, the light source for measuring the Faraday rotation angle _θF is He-
A Ne laser (wavelength 6328 Å) was used. Further, the measurement was performed by transmitting light through the thin film 11.

In the above embodiment, the thin film 11 is oriented and grown on the BaF ₂ film 6 due to the lattice constant of (Y, Bi) ₃ (Fe, Al) ₅ O ₁₂ (which varies depending on the amount of Bi substitution) that constitutes the thin film 11. For example, 12.42 Å) is almost twice the lattice constant of BaF ₂ (6.187 Å), and BaF ₂ and (Y,
This is because the lattice misfit with Bi) ₃ (Fe, Al) ₅ O ₁₂ is extremely small. Furthermore, in general, the lattice constant of Bi-substituted rare earth iron garnet R _3-x Bi _x (Fe,M) ₅ O ₁₂ is 12.30 depending on the type of R and the Bi substitution amount x.
It is known to vary in the range of ~12.54 Å,
From this, by appropriately selecting the type of R and the Bi substitution amount x, it is possible to make the above-mentioned misfit substantially zero. Nao (111)
The Bi-substituted rare earth iron garnet thin film grown in the direction of 2 shows good magnetic properties because the growth direction is the garnet's easy axis of magnetization.

In the above embodiment, the sputtering method was used to form the thin film 11, and polycrystalline iron garnet represented by the compositional formula Bi _2.0 Y _1.0 Fe _3.8 Al _1.2 O ₁₂ was used as the target material. However, the target composition is not limited to this, and may be a mixture containing each of the elements included in the above-mentioned compositional formula, for example. More generally, (Bi ₂ O ₃ ) _x (R ₂ O ₃ )
A material consisting of an oxide containing at least Bi atoms, Fe atoms, and rare earth atoms, as represented by _y (Fe ₂ O ₃ ) _z (M ₂ O ₃ ) _u , can be used. Here, 0
<x≦3/2, 0<y≦3/2, 0<z<5/
2, 0≦u≦5/2. Further, R is a rare earth element such as Y or Sm, and M is Al ³⁺ , Ga ³⁺ , Sc ³⁺ ,
Tl ³⁺ , (Co ²⁺ +Ti ⁴⁺ ), etc.

Further, in the above embodiment, the quartz glass substrate 2 was used as the substrate on which the BaF ₂ film 6 was formed, but other types of glass, such as alumina silicate glass (for example, Corning 1723), silicate glass (for example, glass such as Vycor glass), borosilicate glass (e.g. Pyrex glass) or _SiO2
Of course, it is possible to use amorphous substrates made of materials such as stainless steel (including anodized metals), semiconductors such as Si, insulators such as BN, and crystalline substrates such as ceramics such as alumina. may also be used. Furthermore, in the above embodiment, the BaF ₂ film 6 was used as the film on which the thin film 11 was to be formed, but the thin film 1
Other types of films other than BaF ₂ film 6 may be used as long as BaF 2 film 1 can be grown oriented, and generally BaF ₂
Part of Ba in the membrane was replaced with Sr or Ca
A Ba _1-xy Sr _x Ca _y F ₂ film (0≦x+y<1) may also be used.

Further, in the above embodiment, _a vacuum evaporation method was used to form the BaF ₂ film 6, but more generally, the Ba _1-xy Sr _x Ca _y F ₂ film is formed using a sputtering method, for example. , other vapor phase growth methods such as CVD method, etc. can be used. Similarly, in the above embodiments, the sputtering method was used to form the thin film 11, but other vapor phase growth methods such as evaporation, CVD, and ion plating, or liquid phase epitaxial methods ( LPE method) etc. may also be used.

Further, the substrate temperature when forming the BaF ₂ film 6 and the thin film 11 is not limited to the temperature in the example, and other temperatures may be used as long as the BaF ₂ film 6 and the thin film 11 are grown in the orientation. . but,
When the substrate temperature when forming the BaF ₂ film 6 is below 550°C or above 800°C, the BaF ₂ film 6, generally Ba _1-xy Sr _x
Since it is difficult to grow Ca _y F ₂ film oriented, 550
Preferably the temperature is ~800°C. In addition, when the substrate temperature when forming the thin film 11 is 350°C or lower, the thin film 11 is
1 becomes an amorphous film without directional growth,
At temperatures above 700°C, the vapor pressure of Bi increases, making it difficult to obtain a thin film 11 with a large Bi substitution amount x.
Preferably the temperature is 350-700°C.

In the above example, a (Y, Bi) ₃ (Fe, Al) ₅ O ₁₂ thin film was used as the garnet thin film, but rare earth garnet is generally used.
Other types of garnet thin films such as R ₃ M ₅ O ₁₂ (including those in which R or M is partially replaced with other elements), gadolinium gallium garnet (GGG), etc. may also be used.

As described above, according to the garnet thin film element according to the present invention, since the garnet thin film is provided particularly on the Ba _1-xy Sr _x Ca _y F ₂ film (0≦x+y<1), it has extremely good performance. A garnet thin film element having perpendicular magnetization characteristics can be provided.

Further, according to the method for manufacturing a garnet thin film element according to the present invention, in particular, a Ba _1-xy Sr _x Ca _y F ₂ film (where 0≦
Since the garnet thin film is grown azimuthally on the substrate (x+y<1), it is possible to manufacture a garnet thin film element with extremely good perpendicular magnetization characteristics, and since a variety of substrate materials can be selected, the manufacturing process is easy. This is extremely convenient.

[Brief explanation of drawings]

1A and 1B are cross-sectional views showing one embodiment of the method for manufacturing a garnet thin film element according to the present invention in the order of steps, and FIG. 2 is a garnet thin film manufactured by the embodiment shown in FIGS. 1A and 1B. It is a graph showing the hysteresis characteristics of the (Y, Bi) ₃ (Fe, Al) ₅ O ₁₂ thin film that constitutes the device. 3. In the symbols used in the drawings, 1... sample stage, 2... quartz glass substrate, 3... filament, 4... BaF ₂ , 5, 10... heater, 6...
BaF ₂ film, 7... Electrode plate (sample stand), 8... Electrode plate, 9... Target, 11... (Y, Bi) ₃
(Fe, Al) ₅ O ₁₂ thin film.

Claims (1)

[Claims] 1. Ba _1-xy Sr _x provided on a predetermined substrate
Ca _y F ₂ film (0≦x+y<1) and this
A garnet thin film element comprising a garnet thin film provided on a Ba _1-xy Sr _x Ca _y F ₂ film. 2 Ba _1-xy Sr _x Ca _y F ₂ film (however, 0
≦x+y<1), and then the above
1. A method for manufacturing a garnet thin film device, characterized in that a garnet thin film is oriented and grown on a Ba _1-xy Sr _x Ca _y F ₂ film.