JPH0459280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic garnet liquid phase epitaxial single crystal containing bismuth (Bi) grown on a garnet single crystal substrate.

[Prior art]

In optical communications, it is known that reflected return light entering a laser diode, which is a light source, deteriorates the quality of transmission. In order to solve this problem, as reported by Kobayashi and Ueki et al. in Technical Research Report OQE78-133, Journal of the Institute of Electronics and Communication Engineers,
In the 1.3 μm band, it has been proposed to use an optical isolator using yttrium-iron-garnet as a Faraday rotator.

[Problems with conventional technology]

The optical isolator material is required to have a lower absorption loss than the conventional yttrium-iron-garnet at the wavelength of light used, and a higher Faraday rotation ability. Garnet containing Bi as a solid solution is known as a material that satisfies these conditions. The material properties of this Bi solid solution garnet are described, for example, in the paper by Takeuchi et al., Japanese Journal of Applied Physics.
Physics), Volume 12 (1973), p. 465, and the paper by Uitzkok et al., AIP Conference Proceedings.
Proceedings) Volume 10 (1972) Page 1418, etc.

The magnitude of the magneto-optical effect, or Faraday rotation ability, exhibited by garnet crystals is due to the Bi dissolved in the crystal.
increases with the amount of However, even if it is attempted to dissolve a large amount of Bi in solid solution, it is known that there is a limit to the amount of Bi in solid solution. These situations are detailed in the following papers.

For example, Japanese Journal of Applied Physics, No. 13 by Shinagawa et al.
The report on polycrystalline materials (ceramics) in Vol. (1974) p. 1663 is the first example and will be explained below.
Magnetic garnet crystal Re ₃ Fe ₅ O ₁₂ (Re is Sm, Eu,
When Bi is dissolved as a solid solution in one of Gd, Tb, Dy, Y, Er, and Tm, Bi replaces the above element Re, and the composition of Re _3-x Bi _x Fe ₅ O ₁₂ crystals are produced. The limit of the amount of Bi in solid solution differs depending on the type of element Re mentioned above, and the most Bi can be dissolved in solid solution when Re is gadolinium (Gd), that is, when Gd _3-x Bi _x Fe ₅ O ₁₂ So, the upper limit of x is about 1.4. If an attempt is made to increase the amount of Bi beyond this, a phase other than garnet (a substance with a composition and crystal structure other than garnet) will be generated. The results of examining the lattice constant of the produced garnet crystal show that the lattice constant increases with the amount of Bi solid solution, and at x=1.4, the lattice constant is 12.54 Å.

Then, by flux method, Gd _3-x Bi _x Fe ₅ O ₁₂
In the report on the case of growing single crystals by Tamashiro and Tsushima in Proceedings of the 7th Japan Society of Applied Magnetics (1983), pp. 163-164, the solid solubility limit of Bi is smaller than that of polycrystals. When x=about 1.15, the estimated value of the lattice constant in this case is 12.53 Å.

[Purpose of the invention]

The object of the present invention is to solve the problem of the previously known Bi
A Bi solid solute garnet with a magneto-optical effect that is even better than the conventional yttrium-iron-garnet and the previously known Bi solid solute garnet crystals, which have an increased Bi solid solution content than the solid solute garnet crystals. Our goal is to provide single crystals.

[Structure of the invention]

According to the present invention, the lattice constant is 12.53 Å or more 12.64
Liquid phase epitaxial growth using a garnet single crystal having a value of Å or less as a substrate and having a composition formula of Gd _3-x Bi _x Fe ₅ O ₁₂ (1.72≦x≦3). A magnetic garnet single crystal is obtained.

[Principle of the invention]

The principle of the present invention was discovered through experiments by the inventors. That is, using a melt containing a large amount of Bi ₂ O ₃ , Gd _3-x Bi _x with a lattice constant of 12.568 Å
Fe ₅ O ₁₂ (x≧1.72) When growing a liquid phase epitaxial magnetic single crystal, the lattice constant is 12.383 Å.
When we attempted to grow the above epitaxial single crystal using a Gd ₃ Ga ₅ O ₁₂ single crystal as a substrate, no growth of a garnet single crystal film was observed even when the substrate was immersed in a melt below the liquidus temperature. However, when Gd ₃ Sc ₂ Ga ₃ O ₁₂ with a lattice constant of 12.567 Å was used as a substrate, a garnet single crystal film was obtained. In other words, in order to obtain a liquid-phase epitaxial magnetic garnet single crystal film with a large lattice constant containing a large amount of Bi as a solid solution, the lattice constant of the substrate must also correspond to this, and the lattice constant mismatch is large. In some cases, it is not possible to grow a garnet film on the substrate.

〔Example〕

Examples of the present invention will be described in detail below.

(Example 1) A Gd ₃ Sc ₂ Ga ₃ O ₁₂ nonmagnetic single crystal wafer was used as the substrate crystal. This wafer was fabricated from a raw stone that was pulled and grown in the <111> direction from a melt having the same composition by a rotational pulling method.The lattice constant of this wafer is 12.567 Å, and the plane orientation of this wafer is { 001} plane, the diameter of this wafer is 25 mm. For this wafer, gadolinium oxide (Gd ₂ O ₃ ) 0.4029 mol %, iron oxide (Fe ₂ O ₃ ) 7.5971 mol %, lead oxide (PbO) 65.7143 mol %
Using a melt with a composition of 26.2857 mol% bismuth oxide (Bi ₂ O ₃ ), liquid phase epitaxial growth was performed for 35 minutes at 680°C with a supercooling temperature of 30°C in a platinum crucible with a depth and inner diameter of 50 mm. Summer. As a result,
A homogeneous magnetic garnet single crystal film (Gd _3-x Bi _x Fe ₅ O ₁₂ ) containing Bi as a solid solution with a thickness of 40 μm was obtained on the wafer. The lattice constant in this garnet film was measured by the X-ray diffraction bond method. In this result, the lattice constant was 12.568 Å. When the Bi solid solution amount x was analyzed using an X-ray microanalyzer, it was found that x=1.72.

(Example 2) A Nd ₃ Ga ₄ Mg _0.5 Zr _0.5 O ₁₂ nonmagnetic single crystal wafer was used as the substrate crystal. This wafer is
It was produced by pulling and growing a melt having the composition Nd ₃ Ga ₄ Mg _0.6 Zr _0.4 O ₁₂ in the <111> direction using the pulling method, and then cutting out a portion of the melt. The lattice constant of the wafer is 12.603 Å, and the plane orientation is {110} plane diameter.
It is 23mm. Using this wafer, the composition
Gd ₂ O ₃ 0.3525 mol%, Fe ₂ O ₃ 6.6475 mol%,
A melt containing 66.4286 mol% of PbO and 26.5714 mol% of Bi ₂ O ₃ was used in a platinum crucible with a depth and inner diameter of 50 mm.
Liquid phase epitaxial growth was performed at 640°C with a supercooling temperature of 80°C. In a growth time of 20 minutes, a homogeneous magnetic garnet single crystal film with a thickness of 30 μm containing Bi dissolved therein was obtained on the substrate wafer. As a result of measuring the lattice constant of this crystal film, it was 12.602 Å, and as a result of analyzing the amount of Bi solid solution, x = 2.5, that is, the composition formula
It was Gd _0.5 Bi _2.5 Fe ₅ O ₁₂ .

(Example 3) The substrate crystal is Sm ₃ Sc ₂ with a lattice constant of 12.64 Å.
A Ga ₃ O ₁₂ nonmagnetic garnet single crystal wafer parallel to the {111} plane was used. The diameter is 23mm. Gd ₂ O ₃ 0.0147 mol%, Fe ₂ O ₃ on this substrate
5.4386 mol%, PbO59.5294 mol%, _{Bi2O3 35.0173}
Liquid phase epitaxial growth was performed using a mol % melt in a platinum crucible with a depth and inner diameter of 50 mm at 610°C and a supercooling temperature of 130°C. After a growth time of 20 minutes, a homogeneous magnetic garnet single crystal film with a thickness of 70 μm containing Bi dissolved therein was obtained on the substrate wafer. The lattice constant of this crystal film is 12.635 Å, and the amount of Bi solid solution is x =
3.0, that is, the compositional formula Bi ₃ Fe ₅ O ₁₂ was obtained.

(Example 4) The substrate crystal has a lattice constant of 12.530 Å.
Gd _0.39 Tb _2.61 S _c2 Ga ₃ O ₁₂ A nonmagnetic garnet single crystal wafer parallel to the {111} plane was used. The diameter is 23mm. On this substrate, Gd ₂ O ₃ 0.3828 mol%, Fe ₂ O ₃ 7.2172 mol%, PbO6 2.4286 mol%,
A melt containing 24.9714 mol% of Bi ₂ O ₃ and 5.0000 mol% of B ₂ O ₃ was heated at 720°C in a platinum crucible with a depth and inner diameter of 50 mm.
Liquid phase epitaxial growth was carried out at a supercooling temperature of 60℃. Growth time 15 minutes, on the substrate wafer
A homogeneous magnetic garnet single crystal film containing Bi as a solid solution with a thickness of 40 μm was obtained. The lattice constant of this crystal film was 12.568 Å, and the amount of Bi solid solution was x=1.72.

In the above examples, the amount of Bi solid solution in each of the obtained garnet single crystal films containing Bi solid solution was as follows:
This amount is larger than the amount of Bi solid solution in the conventionally obtained garnet single crystal, and the amount corresponds to the size of the lattice constant of the substrate crystal. In addition, in the above example, 4
Although we have explained the types of substrate crystals, garnet single crystals with other compositions can be used as substrates as long as they have a lattice constant value of 12.53 Å or more and 12.64 Å or less, and the composition formula is Gd _{3- x} Bi _x
A liquid phase epitaxial magnetic garnet single crystal with Fe ₅ O ₁₂ (1.72≦x≦3) can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to increase the amount of Bi solid solution compared to the conventional yttrium-iron-garnet crystal and the previously known Bi solid solution garnet crystal.
It is possible to obtain a Bi solid solution garnet single crystal which has a magneto-optical effect that is even better than that of a solid solution garnet crystal.

Claims (1)

[Claims] 1 A garnet single crystal with a lattice constant of 12.53 Å or more and 12.64 Å or less is used as a substrate and is grown by liquid phase epitaxial growth on the substrate, and the composition formula is Gd _3-x.
Liquid phase epitaxial magnetic garnet single crystal with Bi _x Fe ₅ O ₁₂ (1.72≦x≦3).