JPS62216310A - Magneto-optical crystal growth method - Google Patents

Abstract

PURPOSE:To grow a magneto-optical crystal having less variation in characteristics in a film thickness direction by holding the melting of a melt at high temperature for a predetermined time, then reducing the temperature, holding it for a predetermined time, melting it, then further decreasing the temperature and the crystal is formed on a substrate by liquid growth. CONSTITUTION:When a thick film of Bi-substituted garnet crystal is formed on a nonmagnetic garnet substrate by liquid growth, the melting of a melt is held at high temperature T1 from t1 to t2, then held at temperature T2 from t3 to t4 to melt it at two stages, then further the temperature is reduced to T3 to form a crystal on the substrate by liquid growth. In this case, T1 is 1,100+ or -40 deg.C, T2 is 850+ or -50 deg.C and T3 is 730 deg.C. Thus, a magneto-optical crystal having less variation in characteristics in a film thicknesswise direction is grown by an extremely simple method.

Description

[Detailed Description of the Invention] [Summary] A method for growing Bi-substituted garnet crystals with a large magneto-optical effect, in which melting is performed at two temperatures, and then
By lowering the temperature and growing the crystal in a liquid phase on the substrate, it is possible to obtain a magneto-optic crystal with little change in characteristics in the film thickness direction.

[Industrial application field]

The present invention relates to a method for growing Bi-substituted garnet crystals having magneto-optic effects.

Since liquid-phase grown Bi-substituted garnet crystals have a large magneto-optic effect, methods for growing thick films are currently being researched with the aim of using them in magneto-optic elements such as optical isolators.

[Conventional technology]

Conventionally, when growing W films of Bi-substituted garnet crystals, the same melting temperature is used for growth.

[Problem that the invention seeks to solve]

The conventional method described above has the disadvantage that the crystal properties change with the passage of crystal growth time, and the properties of the thick film change in the film thickness direction.

The present invention was created in view of these points, and its purpose is to provide a simple method for growing a magneto-optic crystal with little change in properties in the film thickness direction2).

[Means for solving problems]

FIG. 1 is a diagram for explaining the present invention in detail. In the figure, the vertical axis represents temperature, the horizontal axis represents time, and the curve represents the treatment temperature per hour curve of the present invention. The present invention
When a thick film of BiW-type garnet crystal is grown in liquid phase on a non-magnetic garnet substrate, the melt is maintained at a high temperature T from t to t2 as shown in Fig. 1, and then from t3 to t4. Two steps of melting are performed while maintaining the temperature at T2, and then the temperature is further lowered to T3 to grow crystals on the substrate in a liquid phase.

[For production]

By melting the melt at two temperatures, it is possible to reduce changes in the properties of the thick film in the direction of crystal growth.

〔Example〕

In the embodiment of the present invention, T in FIG. 1 is 1100±40°C, T2 is 850±50°C, and T3 is 730°C.

The characteristics of the magneto-optic crystal formed by this method are
A comparison with a conventional example is shown in FIG.

FIG. 2 shows the dependence of the crystal growth rate Vg on the growth time, and FIG. 3 shows the dependence of the lattice constant mismatch Δa on the growth time. In both figures, the growth conditions are indicated by a white circle (A) using an 80φ crucible and a melting temperature of 1060℃1.
After holding for 2 hours at 900℃, the black circle mark (B) is 55φ
After holding the melting temperature at 1060℃ for 1 hour using a crucible of 900℃
℃ for 2 hours, the white triangle mark (C) uses a 55φ crucible and the melting temperature was held at 1060℃ for 3 hours, the black triangle mark (D) uses a 55φ crucible and the melting temperature was held at 1060℃ for 3 hours. It is something. (A and B above are the present example, and C and D are the conventional example.) Looking at Figure 2, it can be seen that the growth speed Vg decreases as the growth time passes, but the rate of decrease is the same as that of the present invention. It is smaller if the dissolution is performed in stages.

This is particularly noticeable in the case of an 80φ crucible. The fact that the growth rate Vg decreases little means that the Faraday rotation angle θF decreases little, and it can be seen that the method of the present invention is effective. Further, the lattice constant mismatch Δa in FIG. 3 is defined by subtracting the lattice constant of the film from the lattice constant of the substrate, and a large increase in Δa causes crystal cracks, defects, etc., so a smaller one is preferable. In this example, the increase after 3 hours of growth was smaller than in the conventional example, indicating that the method of the present invention is effective.

[Effects of the Invention] As described above, according to the present invention, a magneto-optic crystal with little change in characteristics in the film thickness direction can be grown using an extremely simple method, and is extremely useful in practice.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the present invention in detail, Fig. 2 is a diagram showing the dependence of the crystal growth rate Vg on the growth time, and Fig. 3 is a diagram showing the dependence of the lattice constant mismatch Δa on the growth time. be.

Claims (1)

[Claims] 1. Bi-substituted garnet crystal with large magneto-optical effect (
In the magneto-optic crystal growth method in which a thick film of the rare earth element Bi)_3(FeAlGa)_5O_1_2 is grown in liquid phase on a non-magnetic garnet substrate, the melt is maintained at a high temperature for a certain period of time, then the temperature is lowered and maintained for a certain period of time. A magneto-optical crystal growth method that involves growing crystals on a substrate in a liquid phase by further lowering the temperature after melting.