JPH01152604A - Oxide garnet single crystal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an oxide garnet single crystal, particularly a garnet with a frequency of 100
The present invention relates to an oxide garnet single crystal that is useful as a new magnetic film for microwave elements 1 such as isolators and circulators used in the microwave band from MHz to several tens of GIk.

(Conventional technology and its problems) Conventionally, YIG crystals grown by the flux method have been used as magnetic materials for microwave devices, but microwave devices made by the flux method are said to be expensive to manufacture. Because of this disadvantage, it has been proposed to use a WIG crystal grown by a liquid phase epitaxial method applying a wafer process technology developed in the semiconductor industry.

However, this YIG crystal has a drawback that the temperature dependence of the resonance frequency becomes large when constructing a microwave element due to the large temperature dependence of saturation magnetization.
Some of the iron in the composition of the YIG crystal is replaced by G, which becomes non-magnetic ions.
It has been reported that the iron in the WIG crystal is replaced with Ga, but when some of the iron in the WIG crystal is replaced with Ga, a mismatch in the lattice constant between the epitaxial film and the GGG single crystal, which is the substrate crystal, occurs even when the amount of substitution is 0. This mismatch causes an increase in strain and, in extreme cases, the disadvantage that cracks occur in the epitaxial film.

Therefore, for the purpose of matching the lattice constants of the epitaxial film and the substrate crystal.

1) Adding La element with a large ionic radius to the Ebitaxi cell film, 2) Using GG as the substrate crystal, which is normally used for this type of application.
A method has been proposed in which a part of the Gd element in GGG is replaced with a Y element with a small ionic radius to form a (YGd)3Ga,0□ crystal from a G crystal. As the amount of gallium in the Evitaxel membrane increases, it is necessary to increase the amount of Lanthanum in the Ebitaxel membrane.
), it is necessary to increase the yttrium substitution amount in the substrate crystal as the gallium substitution amount in the Ebitaxi cell film increases, but if the yttrium substitution amount increases, cell growth will occur during substrate single crystal growth. It turns out that there is a problem with it being easy.

(Structure of the Invention) The present invention relates to a high-quality material for microwave elements that solves the above-mentioned disadvantages.
-a Ga8-b '12 (here a, b is 0,6≧a
>O13,1≧b〉3.0) on a garnet substrate single crystal with one compositional formula Lax vy-x
Fez Ga8-y-z 012 (two x, y, z
is 0.1>x>0.3.1>y>3.0.4.1>z>
The film is characterized by being formed by growing a film represented by the number 3.6 using Ebitaxicel.

In other words, the present inventors conducted various studies on the development of a microwave element material that does not cause temperature dependence of the resonant frequency, mismatch in the lattice constant between the substrate crystal and the Ebitaxi cell growth layer, and does not cause pits in the grown film. YaGdbaGag-bO12 (a,
b is a relatively small one with a lattice constant in the range of 12.367 to 12.383. ), 01□ also has a small crystal lattice, so mismatching of lattice constants is prevented, and the epitaxial film to be grown on this substrate is La x Yy-x Fe z G" g -y
-z' 12 (""V'2 is as described above)
Then, the z value that defines the amount of iron is 4, 1 > z
> 3, 6, mainly (d) in YIG
Since the iron ions at the site are replaced with non-ionic gallium element, the temperature dependence of the saturation magnetization due to the iron ions at the site (d) can be reduced, and this material can be grown on the substrate described above. Since the lanthanum substitution amount of this product is said to be less than 0.1,
We confirmed that it is possible to grow an epitaxial film that is less prone to pits and has no temperature dependence of saturation magnetization.

Composition of substrate single crystal and epitaxial film used for 2N,
The present invention was completed by conducting research on this manufacturing method.

As described above, the garnet substrate single crystal constituting the oxide garnet single crystal of the present invention has the composition formula 7, where %≧a>Olb is a number expressed by 3.1≧b>3.0, This is (6) Y and Gd on the site, [a]
It is assumed that part of Y and Ga are arranged at the site (d), and Ga is arranged at the (d) site, and an example of this is shown by the formula %. For example, this one is Y, 0
．． 3.5 to 7.5 mol%, Gd, 030 to 34 mol%, and Ga, 0.61 to 63 mol% were placed in a crucible, heated to 1,730°C by high frequency induction to melt, and then extracted from this solution. It can be obtained by pulling a single crystal using the Czochralski method.

When a wafer cut from this single crystal was etched with, for example, hot phosphoric acid and a lattice constant table was measured, it was confirmed that the lattice constant was 12.367 to 12.383.

Furthermore, the structure to be grown on this substrate single crystal has a compositional formula of La Yx y- as described above.
x Fe2Gag-y-z 012, and this x, y,
z is 0, 1>x>O13, 1>y>3.0.
4, 1 > z > 3.6, which means (Q) La and Y at the site, (a) Fe and Y at the site
Part of and part of Ga.

(d) Fe and Ga are placed at the site, and the formula La0102゜3.04"3.79"1.15'12
- "0.IY2.97Fe, □5aax, io□ is exemplified. This one has a lattice constant of 12.363 to 1
2,372 people, but as mentioned above, the lattice constant of the substrate single crystal on which Ebitaxi Cell is grown is 12.
．． 367 to 12.383 people, and the lattice constants of both of them match within the range of ±0.003 people, so there is no mismatch, and Ebitaxicell can be grown easily, and the obtained Ebitaxicell growth layer has no cracks. It doesn't even come in.

Regarding this epitaxial membrane, if this is a conventionally known WIG, this WIG has approximately 2 points at the [8] site.
．． There is an iron ion with a formula weight of 0, and an iron ion with a formula weight of about 3.0 at the [d] site, and since the (a) and (d) sites are mostly occupied by iron ions, the saturation magnetization is about 1. A value of 1.760G corresponding to a formula weight of .0 is produced.

In addition, iron ions at the (d) site make this material have a strong temperature dependence of its saturation magnetization, but the WIG shown by the above compositional formula used in the present invention is mainly (d) ) The iron ions at the site are replaced with gallium element, and the amount Z value of this iron ion is set to 4.1>Z>3.
6, it is said that the saturation magnetization is independent of temperature.

In addition, it is known that lanthanum element is further added to those in which iron ions are replaced with gallium element in this way, and the lanthanum substitution amount X value is set to 0, 24 > x > 0, 13, but (La 'l Fe Ga)s
It was found that if the lanthanum value in the ets crystal was set as above, many bits would be generated in the Ebitaxi cell film, so in the present invention, this X value was set to 0.1〉x〉0, so that bits would not be generated. It has become something that does not exist.

This shrimp taxicel growth can be performed using the liquid phase method.

Therefore this is La103m 'lx', 3, 'eh
oz, Game, and flux components PbO and B
2O, was placed in a platinum crucible, and the temperature was 950 to 1,100'.
The substrate single crystal described above can be immersed in this melt by heating to C to melt it.The thickness of the epitaxial layer produced by this epitaxial cell growth method varies depending on the frequency used in the target microwave device. However, normally it may be in the range of 5p to 40%.

The garnet oxide single crystal of the present invention obtained by the method described above has no temperature dependence of resonance frequency, no mismatch in lattice constant between the substrate single crystal and the epitaxial cell growth layer, and furthermore, the grown epitaxial film has no temperature dependence. Since it does not generate bits, it has excellent physical properties as a material for microwave elements, and this material has a frequency of 1o, for example.

It is said to be useful as a microwave element used in the microwave band from MHz to several tens of GHz, and also as a magnetic film for isolators and circulators.

Next, an example of the present invention will be described. In one example, the measurement of the resonance magnetic field value, the calculation of the saturation magnetization, and the calculation of the temperature coefficient quantitatively indicating the temperature dependence of the saturation magnetization were performed as follows.

[Measurement of resonance magnetic field value]

A small piece of 2.6' x 2.6p intestine was cut out from the sample, and using a ferromagnetic resonance device with a variable temperature device, the resonance magnetic field values were measured when the direction of the applied magnetic field was horizontal and vertical between the epitaxial membrane and the applied magnetic field. Measure while changing the sample temperature.

[Calculation of saturation magnetization]

It is calculated from the resonance magnetic field value measured above using the following formula.

Second, 4πMs...Saturation magnetization.

Ha...Anisotropic magnetic field.

) IL: Resonant magnetic field value when the epitaxial film is placed perpendicular to the applied magnetic field, H++: Resonant magnetic field value when the epitaxial film is placed parallel to the applied magnetic field.

[Calculation of temperature coefficient]

From the graph of the temperature dependence of saturation magnetization for each sample, a temperature coefficient indicating the temperature dependence of saturation magnetization in the range of -30° C. to 80° C. is calculated from the following equation.

(Note) 4π Mg (80°C)...Saturation magnetization at 80°C 4πMg (-30°C)...Saturation magnetization at -30°C Example 1 Ebitaxel/La as a component forming the film, 0
．． , Y, O,, Fa, 03 and Ga, o, are shown in Table 1. Fs, O, and Ga, 0. 8.
Seeds were charged into a platinum crucible in an amount that corresponds to the composition of the shrimp taxicel membrane, and PbO1B as a brax component was added to the platinum crucible.
20. After charging, it is heated to 1,100°C to melt it, and then the formula Y□GdL□Ga4* is added to the melt.
A single garnet substrate wafer represented by sO□ is immersed and the formula (La Y Fe Ga) is applied to its (111) direction.
The lattice constant of the oxide garnet single crystal obtained in this way, the degree of mismatch (human) between the substrate single crystal and the epitaxial film, and the temperature coefficient of the epitaxial film shown by seis were grown to a thickness of about 2 am. The results shown in Table 1 were obtained, and the mismatches in this product were all 0.003 Å or less, causing no practical problems.
In addition, it has been confirmed that this epitaxial film has a small number of bits and is of good quality because the amount of lanthanum replacement is less than 0.1, and the temperature coefficient is also lower than that of YIG, which is 3.2G/'C. Ta.

The attached Figure 1 is a graph showing the temperature dependence of the saturation magnetization of Sample & 5 and the temperature dependence of the saturation magnetization of YIG as a comparative example. It was confirmed that

Example 2 La2O3 as a component for forming an evitaxial film
,Y,O,,Fe,0. and Ga, 0. was charged into a platinum crucible in an amount that would give the eight types of Ebitaxel membrane compositions with varying ratios of Fe2O3, Ga, and O as shown in Table 2.

In addition to this, PbO1n as a flux component, o
.

After charging, it is heated to 1.000°C to melt it, and then formula Y is added to this melt. A garnet substrate single crystal wafer represented by GdL4SGa4140□ is immersed and the formula (La Y Fe Ga) sets in its (111) orientation.
An epitaxial film shown in was grown to a thickness of about 2 am.

Next, we investigated the lattice constant of the oxide garnet single crystal obtained in this way, the degree of mismatch (human) between the substrate single crystal and the epitaxial film, and the temperature coefficient, and the results shown in Table 2 were obtained. Therefore, in both cases, the mismatch is 0.003 Å or less, which poses no problem in practice.

This epitaxial membrane has a lanthanum substitution amount of 0.02 formula weight and less than 0.1 mass, so it is of good quality with a small number of pits, and furthermore, the temperature coefficient is 0.7G/"C.
It was confirmed that the size was as small as the following.

Example 3 La, O as components for forming an evitaxial film
,,Y,03,Fe,0. and Ga, 0. are shown in Table 3 for Fe2O, Ga, 0. Eight types of Ebitaxicel membrane compositions were prepared by changing the proportions of PbO and 820.
are charged, then heated to 950°C to melt them, and a garnet substrate single crystal wafer represented by the formula YasGdLtxGa4*5Oxz is immersed in this melt to obtain its (
111) direction, an epitaxial film shown in Table 3 was grown to a thickness of about 2p.

Next, we investigated the lattice constant of the oxide garnet single crystal obtained in this way, the mismatch degree (human) between the substrate single crystal and the epitaxial film, and the temperature coefficient of this material, and the results are shown in Table 3. The mismatch was less than 0.003 Å in all cases, so there was no problem in practical use, and the epitaxial film was of good quality with a degree of lanthanum substitution of 001 and a small number of bits. It was confirmed that the material had excellent physical properties since the temperature coefficient was 0.7 G/'C or less.

Comparative example 1 Form an epitaxial film a, 01, V, O,.

Fe, 03 and Ga, 0. , a large amount of Fe and Ga in the epitaxial film crystal, Fe3.86 type large amount of Ga where Ga has no temperature dependence of saturation magnetism.
La is added to a platinum crucible in an amount that gives a formula weight of 1.10, and La is added in an amount that varies its stratification within the range shown in Figure 2, and to this, PbO, B, 0 as flux components are added.
After charging this, it is heated to 1,100°C to melt it, and then a GGG single crystal wafer represented by the formula GaLaaGa4stOsi is immersed in this melt to obtain the (111
) method, an epitaxial film represented by the formula (La Y Fe Ga) eomi is grown to a thickness of about 2 μ-, and the lattice constant of the obtained oxide garnet single crystal and the number of pits present in the epitaxial film are calculated as follows: Upon investigation, the results shown in Figure 2 were obtained. In order to prevent mismatch between the GGG single crystal and the epitaxial film, La 0.
I have to make it 19.

In this case, the number of pits increases in the Ebitaxi cell film, causing a practical problem. Therefore, using GGG as a substrate material and using the formula (La Y Fe Ga) sots
It was confirmed that when the epitaxial film shown by is grown with epitaxial cell growth, it is not possible to eliminate the temperature dependence of saturation magnetization and the mismatch of the lattice constant, and furthermore, it is impossible to grow an epitaxial film with a small number of pits. - Comparative Example 2 Large amounts of Fe and Ga in the epitaxial film crystal were replaced with Fa.

Fa3.Ga is in a range where the saturation magnetic field has no temperature dependence.
86 formula weight, Ga 1.10 formula weight, Y has a formula weight of 3.04, O,, Fe, 0. and Ga, 0. By charging PbO and 8,0 as flux components into a platinum crucible, heating it to 1,000°C to melt it, and changing the amount of Y substitution in this melt within the range shown in Figure 3. Formula (Y Gd Ga) with changed lattice constant, 0
A garnet single crystal substrate indicated by 13 was immersed.

In that (Lit) direction, the formula Yz, oJ! 3. s@Gam,
When the epitaxial film represented by toOxa was grown on the epitaxel, the formula (Y Gd Ga), 0□
The results shown in Figure 3 were obtained regarding the relationship between the Y formula content of the substrate material and the lattice constant as shown in 8, and the relationship between the dislocation density of the epitaxial film. In order to make it within a practical range, it is necessary to make the Y formula weight of the substrate material 0.5 or less,
This substrate material has a lattice constant of 12.
360, it is 0.004 larger than the lattice constant of an epitaxial film with desirable temperature characteristics. Therefore, the equation (Y adGa
)-oxz on a garnet single crystal with the formula YL6
4FeLatGa1. The line width of the ferromagnetic resonance absorption spectrum of the oxide garnet single crystal grown with the epitaxial film shown as llio1m is 5. OOe, which is twice as large as the value 2.50e at which no lattice constant mismatch is allowed, so a mismatch occurs, and in this case there is no temperature dependence of saturation magnetization, and furthermore, the number of pits is It was confirmed that it was not possible to obtain a small epitaxial film.

[Brief explanation of the drawing]

FIG. 1 shows a garnet single crystal substrate prepared in Example 1 with the formula (La Y Fe Ga), 01. Figure 2 is a graph showing the temperature characteristics of the saturation magnetization of the oxide garnet single crystal of the present invention made by growing the epitaxial film shown in FIG. In Example 1, the formula (La Y
FIG. 3 is a diagram showing the relationship between the La formula content and the lattice constant of the oxide garnet single crystal obtained by growing the epitaxial film represented by FeGa)sOtx with the lattice constant. The relationship between the Y formula content and the lattice constant of the substrate material of the oxide garnet single crystal obtained by epitaxially growing an epitaxial film represented by the formula 'ILO4Few,sGa1゜1oots on the garnet single crystal substrate represented by This figure shows a relationship diagram with the dislocation density of the film. □ Temperature (0C) Q O, I
O,? -La expression amount 0: Pit 1 +7 or not? 1 Animal power V Mitome Ure r February 0: Pirido fluffy τ・1 Hungerless waist・: Unusual moon laughter with Pit power

Claims (1)

[Claims] 1. Compositional formula YaGd_b_-_aGa_8_-_bO_
1_2 (here, a and b are 0.6≧a>0.3.1≧b>
3.0) on a garnet substrate single crystal having the compositional formula La_xY_y_-_xFe_zGa_8_-_y_-
_zO_1_2 (here, x, y, z are 0.1>x>0,
3.1>y>3.0, 4.1>z>3.6) A garnet oxide single crystal is formed by epitaxially growing a film.