JP2002362997A - Method for treating iron garnet single crystal, iron garnet single crystal, microwave device and optional device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating an iron garnet single crystal, by which magnetic characteristics and the transmissibility of a bulk iron garnet single crystal can be improved. SOLUTION: The method of treating the iron garnet single crystal comprises heat treating the grown bulk iron garnet single crystal at a temperature of >=1,000 and <=1,500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an iron garnet single crystal, an iron garnet single crystal, a microwave device and an optical device, and more particularly to a method for treating an iron garnet single crystal used for a microwave device and an optical device. About.

[0002]

2. Description of the Related Art An iron garnet single crystal is generally a material having a garnet structure containing yttrium and iron as main components, and microwave devices have been studied by utilizing its high resonance. Typical examples thereof include an isolator, a circulator, and an S / N (signal / noise ratio) enhancer that is a magnetostatic wave element. On the other hand, devices utilizing the translucency in the infrared region, the Faraday effect, and the Kerr effect of iron garnet single crystals are also used in optical communication fields and various types of light as represented by optical networks, which have been receiving attention in recent years. Is being put into practical use with existing sensors. Examples include optical isolators, attenuators, Faraday rotators, optical modulators, magnetic field sensors, current sensors, and the like. Thus, iron garnet single crystal,
It has become a very important key material. 2. Description of the Related Art Conventionally, iron garnet single crystals have been produced, for example, by a floating zone method (hereinafter referred to as “FZ method”) and a liquid phase epitaxial method (hereinafter referred to as “LPE method”) as disclosed in Japanese Patent Application Laid-Open No. 6-48883. ), The flux method and the FZ method using laser heating (hereinafter referred to as “LHFZ method”). Flux method and LP
In the E method, an iron garnet single crystal is grown under conditions close to an equilibrium system, and thus the obtained iron garnet single crystal has high crystallinity and high quality.
Even with the E method, the growth rate is as low as about 10 to 30 μm / hour. Further, in the flux method and the LPE method, an iron garnet single crystal is grown on an expensive single crystal substrate, and a growth-induced magnetic anisotropy occurs because the film is in the form of a film. In many cases, there is a problem in the use of. Therefore, many attempts have been made to reduce the magnetic anisotropy. For example, JP-A-6-770
No. 81 and the like show that bismuth (Bi) -substituted YIG produced by the LPE method is heat-treated in an oxygen-containing atmosphere at 800 to 1200 ° C. In addition, it has been shown that stress-induced magnetic anisotropy of all epitaxial films is reduced by annealing at a temperature of 1200 ° C. or more (refer to “Bubble Technology Handbook”, edited by Technical Committee on Foam Magnetic Domain, Institute of Electrical Engineers of Japan). Publishing, Showa 51
Year). On the other hand, in the FZ method and the LHFZ method, the iron garnet single crystal has a high growth rate of about 1 to 10 mm / hour and has high productivity, and the grown iron garnet single crystal becomes cylindrical due to surface tension. It has the feature that it can be used as a device only by processing the end face. Further, an iron garnet single crystal grown by the FZ method or the LHFZ method is particularly useful for an optical device because of its excellent coupling with an optical fiber. The inventors of the present invention have disclosed the technology of an iron garnet single crystal containing cerium (Ce) as a substitute for a Bi-containing iron garnet single crystal, which has been difficult to produce by the FZ method or the LHFZ method. 9-320848),
It reveals a large Faraday rotation angle. Further, the inventors have disclosed an SSFZ method for growing a decomposition-melting type iron garnet single crystal in a desired orientation (Japanese Patent Application Laid-Open No. H10-251088).

[0003]

However, the FZ method and the L
The iron garnet single crystal obtained by the HFZ method has a problem that the light absorption coefficient increases, and when used as an optical device, the light transmission loss increases and a problem occurs. In addition, the iron garnet single crystal obtained by the FZ method or the LHFZ method has a relatively large magnetic resonance half width (ΔH) indicating the magnetic characteristics, and has a disadvantage that the microwave transmission loss is large even when used as a microwave device. Was. Further, as for the heat treatment, the effect of improving the magnetic anisotropy introduced during the film growth by the LPE method is apparent as described above, and the FZ method and the LH method
There was no study on single crystals grown by the FZ method.

[0004] Therefore, a main object of the present invention is to provide a method of treating a bulk iron garnet single crystal, which can improve the magnetic properties and translucency of the iron garnet single crystal. Another object of the present invention is to provide a bulk iron garnet single crystal having good magnetic properties and translucency. Yet another object of the present invention is to
An object of the present invention is to provide a microwave device using the iron garnet single crystal having good magnetic properties. Still another object of the present invention is to provide an optical device using the iron garnet single crystal having good translucency. In the present invention, the term “bulk body” refers to a non-membrane shape. That is, in the present invention, the bulk body is not a film-like body grown by the LPE method or the like, but is, for example, a lump, a columnar, a rod-like, a plate-like, or a fiber-like grown by the FZ method or the LHFZ method. Means

[0005]

An iron gar according to the present invention
The processing method of the net single crystal is based on the iron
Of iron garnet single crystal by heat treatment of iron net single crystal
A method comprising: subjecting an iron garnet single crystal to at least 1000 ° C.
Iron garnet single crystal heat-treated at a temperature of 500 ° C or less
Processing method. Single iron garnet according to the present invention
The crystal is a bulk iron garnet single crystal,
Iron gar that has been heat treated at a temperature between 0 ° C and 1500 ° C
It is a net single crystal. The microwave device according to the present invention
The chair uses the iron garnet single crystal according to the present invention.
Also, a microwave device. Option according to the present invention
The tical device is an iron garnet unit according to the present invention.
This is an optical device using a crystal. In addition, this
In the invention of the present invention, the iron garnet single crystal
YIG (Y _Three Fe_Five O₁₂) Single crystal and Y site
Is a rare-earth substituted YIG single crystal,
Iron garnet single crystal in which site is replaced by Al, Ga, In
And the like. Further, in the present invention, the heat treatment
The atmosphere is preferably under atmospheric pressure or under pressure.
Preferably contains oxygen. In addition, the atmosphere of heat treatment
The oxygen concentration in the atmosphere is preferably 10% or more, more preferably.
Or more than 50%. Further, the temperature of the heat treatment is 1
The effect of the present invention appears at 000 ° C. or higher,
Preferably, the temperature is higher than 1300 ° C. Also heat treatment
Temperature exceeds 1500 ° C, iron garnet single crystal
Since the decomposition reaction starts, a problem occurs.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.

[0007]

(Embodiment 1) LHFZ shown in FIG.
Using a growing apparatus, unsubstituted YIG of Y ₃ Fe ₅ O ₁₂ was used as a raw material rod. LHFZ growing apparatus 10 shown in FIG.
Includes a quartz chamber 12. An upper moving shaft 14 and a lower moving shaft 16 are provided at the upper and lower portions of the quartz chamber 12, respectively. A raw material rod or a single crystal fiber 18 is provided on the upper moving shaft 14 and the lower moving shaft 16.
Are supported movably in the up-down direction. A laser 20 and a lens 22 are provided on both sides of the quartz chamber 12.
Are provided, and the raw material rod 18 is irradiated with the laser beam 24. The portion of the raw material rod 18 irradiated with the laser beam 24 becomes a molten portion 26. An auxiliary heating portion 28 is provided near the melting portion 26 of the raw material rod 18. With this LHFZ growing apparatus 10, the growing speed is 4
A YIG single crystal in the <111> orientation was grown by the SSFZ method at 0 mm / hour to obtain a bulk iron garnet single crystal. Thereafter, the obtained iron garnet single crystal was subjected to a heat treatment at a processing temperature from 800 ° C. to 1500 ° C. while flowing industrial oxygen at 500 cc / min under atmospheric pressure. The oxygen concentration of the industrial oxygen is 98% or more. Similarly, the obtained iron garnet single crystal was subjected to a heat treatment at a processing temperature of 1300 ° C. while flowing air having an oxygen concentration of 20% at 500 cc / min. Then, ΔH of the heat-treated iron garnet single crystal is expressed by ES
It was measured in the X band using R. Table 1 shows the results.

[0008]

[Table 1]

From the results shown in Table 1, the ΔH characteristics of the bulk iron garnet single crystal are improved by heat-treating the bulk iron garnet single crystal at a temperature of 1000 ° C. to 1500 ° C. as compared to before the treatment. (Decrease in value) was observed.

(Embodiment 2) Using the FZ growth apparatus shown in FIG. 2 and using (Y _2.7 Ce _0.3 ) (Fe _4.7 Ga _0.3
) Was used YIG of O _12. The FZ growth apparatus 30 shown in FIG. Quartz chamber 3
Inside 2, a raw material rod 34, a melt zone 36, a single crystal 38 and a seed crystal 40 are supported so as to be vertically movable. A reflection surface mirror 42 is provided on a side of the quartz chamber 32.
An infrared lamp 44 is provided in the reflection surface mirror 42,
The infrared light of the infrared lamp 44 is directly reflected by the reflecting mirror 4.
2 is reflected and collected on the raw material rod 34. The portion of the raw material rod 34 where the infrared rays are focused becomes a fusion zone 36.
A means (not shown) for adjusting the atmosphere in the quartz chamber 32 is connected to the upper and lower portions of the quartz chamber 32. With this FZ growth apparatus 30, a Ce and Ga co-substituted YIG single crystal was grown at a growth rate of 3 mm / hour to obtain a bulk iron garnet single crystal. Thereafter, while flowing industrial oxygen at a flow rate of 500 cc / min.
The heat treatment was performed at a processing temperature up to 500 ° C. The oxygen concentration of the industrial oxygen is 98% or more. Similarly, an air having an oxygen concentration of 20% is flowed through the obtained iron garnet single crystal at 500 cc / min.
The heat treatment was performed at the processing temperature of. Then, an antireflection coating was applied to the heat-treated iron garnet single crystal, and the light absorption coefficient and the Faraday rotation angle were measured at a wavelength of 1550 nm. Table 2 shows the results.

[0011]

[Table 2]

From the results shown in Table 2, the light absorption coefficient characteristics of the bulk iron garnet single crystal can be obtained by subjecting the bulk iron garnet single crystal to a heat treatment at a temperature of 1000 ° C. or more and 1500 ° C. or less. Improves (decreases value)
It was observed that That is, the translucency of the single crystal was improved. On the other hand, a bulk iron garnet single crystal
It was observed that the Faraday rotation angle of the bulk iron garnet single crystal did not change even when the heat treatment was performed at a temperature of not less than ℃.

Example 3 In Example 1, an iron garnet single crystal heat-treated at 1300 ° C. while flowing industrial oxygen was used as a microwave device as shown in FIG.
Was prepared. The isolator 50 shown in FIG. 3 includes a disc-shaped iron garnet single crystal 52. On the iron garnet single crystal 52, a center conductor 54a,
54b and 54c are provided. These center conductors 5
4a, 54b and 54c are electrically insulated from each other. These center conductors 54a, 54b and 54c
Are used as input / output ports 56a, 56b and 56c, respectively. I / O ports 56a, 56
b and 56c are capacitors 58a and 58c, respectively.
b and 58c are grounded. Further, the input / output port 56c is grounded via the resistor 60. When an external magnetic field is applied to the isolator 50 shown in FIG. 3 as indicated by an arrow Hex in FIG. 3 to measure the isolation characteristics, the insertion loss is 0.5 dB and the isolation is 35.
dB, indicating good characteristics.

Embodiment 4 An iron garnet single crystal which was heat-treated at 1300 ° C. while flowing industrial oxygen in Embodiment 2 was polished to a thickness of 690 μm, and an optical isolator shown in FIG. Was prepared. The optical isolator 70 shown in FIG. At the center of the holder 72, a disk-shaped iron garnet single crystal 74 is arranged perpendicular to the optical axis 75.
In the holder 72, a polarizer 76 is disposed so as to face one main surface of the iron garnet single crystal 74, and the analyzer 7 is provided so as to face the other main surface of the iron garnet single crystal 74.
8 are arranged. Further, permanent magnets 80 are arranged on holder 72 above and below iron garnet single crystal 74, respectively. In the optical isolator 70 shown in FIG. 4, the isolation characteristics were 50 dB or more, the insertion loss was 1.3 dB, and excellent characteristics were exhibited.

[0015]

According to the present invention, the magnetic properties and translucency of a bulk iron garnet single crystal obtained by the FZ method or the LHFZ method can be improved. Further, according to the present invention, a microwave device obtained by the FZ method, the LHFZ method, or the like and using a bulk iron garnet single crystal having good magnetic properties can be obtained. Further, according to the present invention, an optical device obtained by the FZ method, the LHFZ method, or the like and using a bulk iron garnet single crystal having good light transmission properties can be obtained.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one example of an LHFZ growing apparatus used in the present invention;

FIG. 2 is an illustrative view showing one example of an FZ growing apparatus used in the present invention;

FIG. 3 is an illustrative view showing one example of an isolator according to the present invention;

FIG. 4 is an illustrative view showing one example of an optical isolator according to the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 LHFZ growing apparatus 12 Quartz chamber 14 Upper moving axis 16 Lower moving axis 18 Raw material rod or single crystal fiber 20 Laser 22 Lens 24 Laser beam 26 Melting part 28 Auxiliary heating part 30 FZ growing apparatus 32 Quartz chamber 34 Raw material rod 36 Melting zone 38 Single crystal 40 Seed crystal 42 Reflecting mirror 44 Infrared lamp 50 Isolator 52 Iron garnet single crystal 54a-54c Center conductor 56a-56c Input / output port 58a-58c Capacitor 60 Resistor 70 Optical isolator 72 Holder 74 Iron garnet single crystal 75 Optical axis 76 Polarizer 78 Analyzer 80 Permanent magnet

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H099 AA01 BA02 CA11 4G077 AA02 BC22 CE05 FE03 HA01 HA03

Claims (4)

[Claims] 1. A method for treating an iron garnet single crystal in which a grown bulk iron garnet single crystal is subjected to a heat treatment, wherein the iron garnet single crystal is heated at a temperature of 1000 ° C. to 1500 ° C.
A method for treating an iron garnet single crystal, which is heat-treated at a temperature of not more than ° C. 2. An iron garnet single crystal which is a bulk iron garnet single crystal and is heat-treated at a temperature of 1000 ° C. or more and 1500 ° C. or less. 3. A microwave device using the iron garnet single crystal according to claim 2. 4. An optical device using the iron garnet single crystal according to claim 2.