JPS61231712A - Manufacture of garnet film - Google Patents

Abstract

PURPOSE:To decrease the growing speed of a film as well as to reduce the defects caused by the sludge in a liquid solution without reducing the quantity of bismuth in a garnet film by a method wherein the flux containing PbO, MoO3 and Bi2O is used. CONSTITUTION:The film forming speed necessary to obtain the same quantity of bismuth can be decreased by containing Bi2O3, PbO and MoO3 as a flux component when a magnetic garnet single crystal film containing bismuth is epitaxially grown on a non-magnetic single crystal plate in the liquid solution consisting of crystal component and a flux component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for producing a garnet film containing bismuth, which is particularly suitable for high-density magnetic bubble memory elements or magneto-optical elements such as optical isolators. The present invention relates to a method for manufacturing a magnetic garnet film.

[Background of the invention]

A magnetic garnet film containing bismuth has a considerably large uniaxial anisotropy energy due to the bismuth, and at the same time has a large Faraday rotation ability, making it suitable for use in high-density magnetic bubble memory devices with minute bubble diameters of 1 μm or less. It is attracting attention as a bubble material. Furthermore, since this garnet film has a large Faraday rotation ability, it is attracting attention as a material for magneto-optical elements such as optical isolators.

Conventionally, when producing a garnet film containing bismuth by liquid phase epitaxial growth, the flux used was P.
b O-B2O3-B i2O3-based flux, Pb
O-Bi2O, system flux, etc. are known. Journal of Crystal Growth
of Crystal Growth) Vol.
64, p.

275 (1983)
.

P. lages) and W. Thorsdork (v.

1'L B E Growth of Bismuth Substate Gadolinylum Garnet Layers: Systemization of Experimental Results (L P E Tolksdorf)
Growth of Bismuth Substit
utedGadolinium Garnet Lay
ers: Systemization of Exp.
P b 0-B20x-B i
, o, When a garnet film is epitaxially grown using a system flux, the larger the supersaturation temperature ΔT, the larger the amount of bismuth in the film. Here, the supersaturation temperature ΔT is the difference between the saturation temperature T of the oxide melt for garnet film growth and the melt temperature T0 during film growth. It is generally known that the larger ΔT is, the faster the film growth rate G becomes. Therefore, in order to increase the amount of bismuth in the film and increase the uniaxial anisotropy energy or Faraday rotation ability, it is necessary to increase ΔT, and along with this, G
.

When Gt becomes too large, garnet microcrystals tend to precipitate in the melt.

When these microcrystals adhere to the garnet film, normal epitaxial growth is hindered in that area, resulting in film defects.

Also, if G2 becomes too large.

It becomes difficult to precisely control the thickness of the garnet film obtained by epitaxial growth.

The same problem as above occurs when a garnet film is grown using a P b OB x 203 flux.

As mentioned above, with conventional flux, if you try to increase the amount of bismuth in the film, you have to increase the growth rate G of the film, which makes it difficult to obtain a high-quality garnet film. Ta.

By the way, when growing a garnet film that does not contain bismuth, MoO
, -LiMoO, G can be made smaller by using the system flux. However, the case of growing a garnet film containing bismuth has not been considered. Bismuth enters the dodecahedral position of garnet, but it is known that it is very difficult to incorporate into the film during liquid phase epitaxial growth. Therefore, when growing a garnet film containing bismuth, the concentration of Bi2O3 in the melt is generally one to two orders of magnitude higher than that of oxides of elements occupying other dodecahedral positions.
It must be increased by an order of magnitude, so Bi, 03
plays a role as a flux component as well as a garnet component in the melt, and when growing a garnet film containing bismuth, the above MoO3-
LiMoO4-based flux cannot be applied as is.

[Purpose of the invention]

An object of the present invention is to reduce the growth rate of a garnet film without reducing the amount of bismuth in the film. An object of the present invention is to provide a method for producing a garnet film.

[Summary of the invention]

Gd, Ga, O, on the (111) plane were obtained from a melt using pb○-Bi2O3 flux having the composition shown in Table 1.

Figure 1 shows the relationship between the supersaturation temperature ΔT, the film growth rate G, (Fig. 1(a)), and the bismuth amount X in the film (Fig. 1(b)) when a Bi*Y3-+iFe&o1m film is grown on a substrate. Shown below. The saturation temperature of this melt was about 900°C. As seen in FIG. 1, G and X increase almost linearly with ΔT. From this result, when we plot the relationship between G and X, we get the result shown in Figure 2. In order to achieve the above object, it is necessary to reduce G required to obtain the same amount of bismuth based on the relationship shown in FIG. By the way, as mentioned earlier, in the case of a garnet film that does not contain bismuth, Mob, -LiMoO,
By using system flux, conventional Pb0-B2
G2 can be made smaller than in the case of O3-based flux. Therefore, even in the case of a garnet film containing bismuth, it is possible to reduce G by appropriately selecting a flux system. Therefore, the present inventors made the above Pb0-B
By adding various oxides to izOi-based flux, G,
We investigated the relationship between As a result, by using a flux containing PbO, MoO, and Bi2O3,
It has been discovered that the G required to obtain the same amount of bismuth can be reduced.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples.

Example 1 Using the composition shown in Table 1 as a starting composition, flux components (
P b O, B i2O3 ) (7) The relationship between the film growth rate G and the amount of bismuth X in the film was investigated when part of the film was replaced with MOo. In Figure 3, MoO.

With the molar ratio of PbO and PbO as parameters, G, ((a
)) and X ((b) of the same figure) and the relationship between supersaturation temperature ΔT. In this experiment, during liquid phase epitaxial growth, the substrate was rotated at a speed of 60 rpm and reversed every 5 seconds. In addition, in order to keep the saturation temperature T of each melt used in this experiment almost constant (approximately 900°C), the L knee B was set as shown in Table 2.
i, O,, PbO, M o O.

Garnet components other than Y, 03 and Fe,
O.

Adjust the concentration of In addition, the molar ratio of Fe, O, and Y2O in each melt is constant (Fs, ○, /Y20.=3
0) It's Nishishide. Also, the molar number of Bi2O and PbO is
2 The table ratio is also constant (B i, o3/Pb0 = 0.17).

As shown in FIG. 3, by increasing the ratio of M o O and PbO, it is possible to increase X for the same ΔT. This is because when the ratio of Mob and Pbo is increased, the concentration of the garnet component to keep T constant can be reduced.

For this reason, even though the ratio of Bi,03 and PbO is constant, as shown in Table 2, Bi,0° and y,o
It is considered that as the molar ratio of 3 increases, the amount of throat mass in the film increases. Furthermore, Moo.

As the ratio of PbO and PbO increases, G for the same ΔT
, can be made smaller. Due to these two effects.

As shown in FIG. 4, G required to obtain the same amount of bismuth X can be reduced.

Example 2 Bi, (D
ySmLn), -, (FgAQ), 0.2 The relationship between the film growth rate G and the amount of bismuth in the film when Moo is added to the film growth melt in the same manner as in Example 1 is shown below. Examined. Table 3 shows the composition and saturation temperature T of the melt used in this experiment. The substrate used is (111) plane Q d z
G a s Ot x. Further, the substrate rotation speed during liquid phase epitaxial growth was 60 rpm, and the rotation speed was reversed every 5 seconds. As shown in Figure 5, by adding MoO3, P
By using bO-Mo○3-Bi2O3-based flux, the film growth rate G required to obtain the same amount of bismuth X can be reduced.

3rd expression ΣR,O,=Dy20. +Sm20. +Ln, 03, and Dy20. : Sm2O3: Ln, 03=1
:5:11 (molar ratio).

Example 3 Bi, (Sm
The relationship between the film growth rate G and the amount of bismuth X in the film was investigated when Moo3 was added to the Ln)3-, Fa2O3, film growth melt in the same manner as in Example 1. Table 4 shows the composition and saturation temperature T of the melt used in this experiment.

The substrate used has (111) plane N d , Ga , 0
It is 1□. Also, liquid phase epitaxy Table 4 XΣR,03=Sm20. +Luzoa.

S m203: L n, ○, = 2:1 (molar ratio).

The substrate rotation speed during crystal growth was 60 rpm, and the rotation speed was reversed every 5 seconds. As shown in Figure 6, MoO3 added Li
By using a PbO-Mob, -Bi, Ox-based flux, the film growth rate G required to obtain the same amount of bismuth X can be reduced.

Example 4 B using PbO-820,-Bi,○, system flux
i*Y:a-wF8sOszThe relationship between the film growth rate G1 and the amount of bismuth X in the film was investigated when Mo○ was added to the film growth melt in the same manner as in Example 1. . The composition and saturation temperature T of the melt used in this experiment are shown in Table 5. The substrate used was <111) Gd, Ga
, o, □. The substrate rotation speed during liquid phase epitaxial growth was 60 rpm and was reversed every 5 seconds. As shown in Figure 7, by adding Mob3, Pb
O-Mob, -B2O3-B i20. By using a system flux, the film growth rate G required to obtain the same amount of bismuth X can be reduced. In this way, the effect of Mob can be seen even in the case of a flux containing B t Os.

Comparative Example Using LizMo○4 instead of Mob in Example 1, the flux component (p b o , B x z 03)
B i, Y, , F e when replacing a part of
, 0,2 The relationship between the growth rate G of the film and the amount of bismuth X in the film was investigated. In this experiment, the saturation temperature T6 was constant (approximately 90
0°C) in the same manner as in Example 1.
The concentration of e2O2 was adjusted. Further, the substrate rotation speed during liquid phase epitaxial growth was 60 rpm, and the rotation speed was reversed every 5 seconds. As shown in Figure 8, Li, MoO for pbo
As the ratio of 4 increases, the amount of bismuth in the film becomes slightly smaller when the film growth rate is kept constant. In this way, when Li or Moo+ is used as the added flux, no effect is seen as when MoO3 is used.

A feature of the present invention is that pbo is used as a flux component.

It contains Mool and Bi2O3.

Even if a small amount (5 mol % or less of the flux component) of Bz Oz + L l z○, BaO, etc. other than those mentioned above is contained, the effect remains essentially the same.

However, after examining various flux system compositions, we found that the most effective fluxes were pbo-MoO□-Bi, 03 system flux and pbo-Mob, -820°-Bi2O3.
It was a system flux. In these flux systems, if the concentration of M, oO, and other components in the flux components is increased too much, microcrystals other than garnet tend to precipitate in the melt. It is desirable that the concentration of M o O in the flux component is 40 mol % or less.

〔Effect of the invention〕

According to the present invention, when producing a garnet film containing the same amount of bismuth, the film growth rate can be reduced to about 2 times per film compared to the conventional method, which has the effect of reducing defects caused by precipitates in the melt. be. Moreover, there is an effect of increasing the accuracy of film thickness control.

[Brief explanation of drawings]

Figure 1 shows the relationship between supersaturation temperature, film growth rate, and amount of bismuth in the film. Figure 2 shows the relationship between film growth rate and film growth rate. Figure 3 shows supersaturation using M003/PbO as a parameter. Figures 4, 5, 6, and 7 showing the relationship between temperature, film growth rate, and amount of bismuth in the film are for Mo○. Figure 8 shows the relationship between the film growth rate and the amount of bismuth in the film using /PbO as a parameter.
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Claims (1)

[Claims] 1. A method for producing a garnet film in which a magnetic garnet single crystal film containing bismuth is epitaxially grown on a non-magnetic single crystal substrate in a melt consisting of a supersaturated crystal component and a flux component, B as a flux component
A method for producing a garnet film characterized by containing i_2O_3, PbO and MoO_3. 2. The method for producing a garnet film according to claim 1, wherein the flux component further contains B_2O_3 in addition to PbO, MoO_3 and Bi_2O_3.