JP6409708B2 - Method for producing bismuth-substituted rare earth iron garnet crystal film - Google Patents

Description

  The present invention relates to a method for producing a bismuth-substituted rare earth iron garnet crystal film.

  Semiconductor lasers used for optical communications and solid-state lasers used for laser processing, etc., generate laser oscillation when the light reflected from the optical surface or processing surface outside the laser resonator returns to the laser element. It becomes unstable. If the oscillation becomes unstable, signal noise may occur in the case of optical communication, and the laser element may be destroyed in the case of a processing laser. For this reason, an optical isolator is used to block such reflected return light from returning to the laser element.

  Conventionally, as a Faraday rotator used for an optical isolator for a fiber laser, which has recently been attracting attention as an alternative to the conventional YAG laser, a terbium gallium garnet crystal (hereinafter also referred to as TGG), a terbium aluminum garnet crystal ( (Hereinafter also referred to as TAG) has been used.

  However, TGG and TAG have a small Faraday rotation coefficient per unit length, and in order to function as an optical isolator, it is necessary to increase the optical path length to obtain a 45 ° polarization rotation angle, and a large crystal must be used. There wasn't. Moreover, in order to obtain high optical isolation, it is necessary to apply a uniform and large magnetic field to the crystal, so a strong and large magnet was used.

  For this reason, the size of the optical isolator is large. In addition, since the optical path length is long, the laser beam shape may be distorted in the crystal, and an optical system for correcting the distortion may be required. Furthermore, since TGG is expensive, a small and inexpensive Faraday rotator has been desired.

  On the other hand, a bismuth-substituted rare earth iron garnet crystal film (hereinafter also referred to as RIG) used exclusively in the optical communication field can be used to reduce the size significantly. It is.

  Generally, RIG is grown by a liquid phase epitaxial growth method (LPE method).

  When growing RIG by a liquid phase epitaxial growth method, for example, by installing and heating a noble metal crucible containing raw materials in a vertical tubular furnace (hereinafter, LPE furnace), garnet single crystal components such as rare earth and iron, Forms a melt in which the flux components bismuth and lead are dissolved. Then, the crystal is grown by bringing the melt into a supersaturated temperature state where RIG is deposited and contacting and immersing one surface of the non-magnetic garnet substrate which is a seed crystal substrate in the melt (for example, Patent Documents 1 to 5). See).

  Since the temperature for growing RIG (hereinafter referred to as the growth temperature) is a high temperature exceeding 800 ° C., after RIG is grown, it is gradually cooled to near room temperature before being taken out of the LPE furnace.

JP 2012-116673 A JP 2012-116672 A JP 2012-131690 A JP 2012-188302 A JP 2012-188303 A

  However, during slow cooling, the RIG may be cracked or cracked due to the stress change due to the difference in thermal expansion coefficient between the non-magnetic garnet as the seed crystal substrate and the RIG, resulting in a decrease in yield. It was the cause.

  Therefore, in view of the above-described problems of the prior art, in one aspect of the present invention, a bismuth-substituted rare earth iron garnet that can suppress the occurrence of cracks and cracks when grown to room temperature after growing a bismuth-substituted rare earth iron garnet crystal film. An object is to provide a method for producing a crystal film.

In order to solve the above problems, according to one aspect of the present invention, a nonmagnetic garnet substrate is brought into contact with a melt, and a bismuth-substituted rare earth iron garnet crystal film is grown on the nonmagnetic garnet substrate by a liquid phase epitaxial growth method. A method for producing a bismuth-substituted rare earth iron garnet crystal film,
After the growth step of growing the bismuth-substituted rare earth iron garnet crystal film, the cooling step of cooling from the growth temperature to room temperature,
In the cooling step,
The temperature drop rate is 200.0 ° C./hr or less,
And after the completion of the growth step, the crucible containing the melt is moved downward, and then a shielding plate is inserted between the grown bismuth-substituted rare earth iron garnet crystal film and the melt. , the surface of the melt, and the bismuth-substituted rare earth iron garnet crystal film grown than when placed so as to face directly, radiant heat from the melt, the bismuth and grown-substituted rare earth iron garnet crystal The manufacturing method of the bismuth substitution type rare earth iron garnet crystal film comprised so that it may suppress reaching a film | membrane can be provided.

  According to one aspect of the present invention, there is provided a method for producing a bismuth-substituted rare earth iron garnet crystal film capable of suppressing cracks and occurrence of cracks when the bismuth-substituted rare earth iron garnet crystal film is grown and then cooled to room temperature. be able to.

Explanatory drawing of the structural example of the film-forming apparatus in embodiment of this invention. Explanatory drawing of the other structural example of the film-forming apparatus in embodiment of this invention. Explanatory drawing of the other structural example of the film-forming apparatus in embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.

  A configuration example of the method for manufacturing the bismuth-substituted rare earth iron garnet crystal film of the present embodiment will be described below.

In the method of manufacturing a bismuth-substituted rare earth iron garnet crystal film according to this embodiment, a nonmagnetic garnet substrate is brought into contact with the melt, and a bismuth-substituted rare earth iron garnet crystal film is grown on the nonmagnetic garnet substrate by liquid phase epitaxial growth. can do.
And after completion | finish of the growth process which grows a bismuth substitution type rare earth iron garnet crystal film, it can have a cooling process cooled from room temperature to room temperature.
In the cooling step, the temperature drop rate can be set to 200.0 ° C./hr or less. Further, in the cooling process, the radiant heat from the melt is higher than that in the case where the melt surface and the grown bismuth-substituted rare earth iron garnet crystal film are directly opposed to each other. It can be configured to suppress reaching the crystal film.

  Here, first, with reference to FIG. 1A, a configuration example of a film forming apparatus and an outline of a procedure that can be suitably used in the method for manufacturing a bismuth-substituted rare earth iron garnet crystal film (RIG) according to the present embodiment. explain.

  The film forming apparatus 10 in FIG. 1A schematically shows a cross-sectional view in a plane passing through the central axis of a crucible 14 installed in the film forming apparatus 10.

  The film forming apparatus 10 can include a heater 11, and a crucible base 12 is disposed in a region surrounded by the heater 11. A crucible 14 containing the melt 13 is placed on the crucible base 12. A raw material, that is, a raw material, ie, a raw material powder containing a flux component, is put in the crucible 14 in advance, heated by the heater 11, and mixed and stirred as necessary to obtain the melt 13. be able to. The material of the crucible 14 is not particularly limited, and is preferably a material that does not react with the melt 13 and has heat resistance with respect to the temperature of the melt 13. For example, a noble metal such as platinum can be suitably used.

  A substrate support shaft 15 can be disposed on the crucible 14 containing the melt 13, and a seed crystal substrate 16 can be attached to one end of the substrate support shaft 15 in advance. .

  In addition, in the film-forming apparatus 10, it can have arbitrary members as needed. For example, an insulating material, temperature measuring means, atmosphere control means for controlling the atmosphere in the region surrounded by the heater 11, and the like can be provided.

  Then, in the RIG film formation using the film formation apparatus 10 shown in FIG. 1A, while rotating the seed crystal substrate 16 by rotating the substrate support shaft 15 in the direction indicated by the arrow A in the drawing, This can be carried out by lowering the substrate support shaft 15 and bringing the seed crystal substrate 16 into contact with the melt 13. At this time, one surface of the seed crystal substrate 16 facing the melt 13 is immersed in the melt 13. In addition, the rotation direction in Fig.1 (a) is an illustration, and is not limited to the direction of the arrow A. FIG.

  In the conventional RIG manufacturing method, after the RIG film is formed on the seed crystal substrate 16, first, the substrate support shaft 15 is raised upward to separate the seed crystal substrate 16 and the grown RIG from the melt 13. 13 and the seed crystal substrate 16 on which the RIG is formed have the same positional relationship as in FIG. That is, the surface of the melt 13 and the grown RIG are arranged so as to face each other directly. Then, while maintaining the positional relationship between the melt 13 and the seed crystal substrate 16 on which the RIG is formed, the seed crystal substrate on which the RIG is formed is held in the region surrounded by the heater 11, Or the cooling process which cools to room temperature vicinity was performed.

  However, as described above, in the cooling process, cracks and cracks may occur in the grown RIG, which causes a decrease in yield.

  Here, for convenience of explanation, the cooling process in the conventional method for producing a bismuth-substituted rare earth iron garnet crystal film has been described using the film forming apparatus of FIG. However, in a conventional method for producing a bismuth-substituted rare earth iron garnet crystal film, a film forming apparatus that does not include a transport mechanism such as a crucible 14 described later and a shielding plate 17 is used.

  The inventors of the present invention diligently studied a method for suppressing cracks and the occurrence of cracks when a bismuth-substituted rare earth iron garnet crystal film is grown and then cooled to room temperature.

  First, a method of slowing the cooling rate and extending the cooling time was examined. However, although a certain effect can be obtained by slowing the cooling rate, the yield improvement is not sufficient only by slowing the cooling rate. Further, if the cooling rate is made slower than necessary, the cooling time becomes longer, which causes a decrease in productivity.

  As a result of further investigation, the present inventors have found that the radiant heat from the melt 13 causes cracks and cracks in the RIG grown in the cooling process, thus completing the present invention.

  Hereinafter, each process of the manufacturing method of RIG of this embodiment is demonstrated concretely.

  Here, the growth process for growing the bismuth-substituted rare earth iron garnet crystal film will be described first.

  In the growth process, as described above, for example, the film forming apparatus 10 shown in FIG. 1A can be used, and one surface of the seed crystal substrate is fused while rotating the seed crystal substrate 16. It can be carried out by bringing it into contact with the liquid 13.

As the seed crystal substrate, a nonmagnetic garnet substrate can be suitably used as described above. The composition of the nonmagnetic garnet substrate is not particularly limited, and can be arbitrarily selected according to the performance required for the deposited RIG, the lattice constant of the RIG to be deposited, and the like. Specific examples of the nonmagnetic garnet substrate include (CaGd) ₃ (ZrMgGa) ₅ O ₁₂ substrate, Gd ₃ (ScGa) ₅ O ₁₂ substrate, Sm ₃ (ScGa) ₅ O ₁₂ substrate, and La ₃ (ScGa). ) ₅ O ₁₂ substrate or the like can be used. In particular, when a Gd ₃ (ScGa) ₅ O ₁₂ substrate, Sm ₃ (ScGa) ₅ O ₁₂ substrate, or La ₃ (ScGa) ₅ O ₁₂ substrate having a large lattice constant is used, the deposited RIG is in the vicinity of 1 μm band. Since light absorption at a wavelength can be reduced, it can be preferably used. Among them, the Gd ₃ (ScGa) ₅ O ₁₂ substrate has a large lattice constant of about 1.256 nm, and the absorption wavelength of light due to Fe ions in the RIG can be shifted to the short wavelength side. Therefore, the non-magnetic garnet substrate is Gd ₃ (ScGa More preferably, it is a ₅ O ₁₂ substrate.

  The size of the nonmagnetic garnet substrate is not particularly limited, and can be arbitrarily selected according to the size of the crucible 14 to be used, the size of the RIG to be grown, or the like.

  Further, the composition of the melt is not particularly limited, and can be arbitrarily selected according to the composition of the RIG to be formed. The melt can be formed by melting, for example, a solid raw material prepared in advance according to the composition of the RIG to be formed. When forming a melt from a solid raw material, the solid raw material is placed in, for example, a noble metal crucible and heated to a temperature at which the raw material is sufficiently melted, so that the melt has a uniform composition as necessary. It can be formed by mixing and stirring.

For example, in the manufacturing method of the RIG of the present embodiment, the general formula Gd _3-xy Bi _x R _y Fe ₅ O ₁₂ (where R is one or more rare earth elements selected from La, Ce, Pr, and Nd). Thus, the RIG represented by 0 <x, 0 <y) can be suitably manufactured.

For this reason, according to the composition of RIG to grow, the above-mentioned solid-state raw material, for example, Gd ₂ O ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ , and oxidation of the component corresponding to R in the above general formula For example, one or more selected from La ₂ O ₃ , CeO, Pr ₆ O ₁₁ , Nd ₂ O ₃ . In addition, in order to suppress the incorporation of PbO, B ₂ O ₃ as a flux component or Pb added as a flux component into the RIG, CaO can also be included.

  In the growth step, the temperature of the melt is not particularly limited, but when the seed crystal substrate 16 is brought into contact with and immersed in the melt 13, the temperature may be selected so that the melt is supersaturated. preferable.

  The conditions such as the rotation speed of the seed crystal substrate 16 and the growth time in the growth process are not particularly limited, and can be arbitrarily selected according to the composition of the RIG to be grown and the characteristics required for the RIG to be grown. can do.

  Next, the cooling process will be described.

  In the cooling step, it is preferable that the temperature lowering rate (cooling rate) is 200 ° C./hr or less as described above. This is because if the rate of temperature decrease is higher than 200 ° C./hr, the grown RIG may be cracked or cracked. The temperature lowering rate is more preferably 120 ° C./hr or less, and further preferably 80 ° C./hr or less.

  The lower limit value of the cooling rate in the cooling step is not particularly limited, but is preferably 20 ° C./hr or more, for example, and more preferably 50 ° C./hr or more. This is because when the temperature lowering rate is less than 20 ° C./hr, the cooling process takes time and the productivity may be lowered.

  Then, during the cooling process, the radiant heat from the melt is increased compared to the case where the melt surface and the grown bismuth-substituted rare earth iron garnet crystal film are directly opposed to each other. It is preferable to configure so as to prevent reaching the garnet crystal film.

  According to the study by the inventors of the present invention, it is possible to prevent the RIG from being cracked or cracked by suppressing the radiant heat from the melt from reaching the grown bismuth-substituted rare earth iron garnet crystal film. This is because it can be suppressed.

  In particular, it is preferable that the radiant heat from the melt to the grown RIG is blocked during the cooling process, that is, the grown RIG is not subjected to radiant heat from the melt.

  The method of configuring so that the radiant heat from the melt reaches the grown RIG is more limited than the case where the melt surface and the grown RIG are arranged so as to directly face each other. Rather, you can choose any method. For example, as shown to Fig.1 (a), the method of comprising so that the shielding board 17 can be inserted in the lower part of the heater 11, and the crucible 14 etc. can be moved is mentioned.

  In the case of the example shown in FIG. 1A, after the growth process is completed, the crucible 14 containing the melt 13 and the crucible base 12 may be moved downward along the block arrow 101 by a transport mechanism (not shown). it can. And after moving the crucible 14 etc. below the lower end part of the heater 11, the shielding board 17 which is a shielding object is moved along the block arrow 102, and the melt 13 is shown in FIG.1 (b). And a shielding plate 17 between the seed crystal substrate 16 on which the RIG is formed.

  By setting it as the state shown in FIG.1 (b), it can comprise so that the radiant heat from the melt 13 may be interrupted | blocked by the shielding board 17, and may not reach to the seed crystal substrate 16 in which RIG was formed. For this reason, it can suppress that the radiant heat from the melt 13 reaches | attains the grown RIG rather than the case where it arrange | positions so that the surface of the melt 13 and the grown RIG may face directly.

  Then, by controlling the output of the heater 11 in the state shown in FIG. 1B, it is possible to cool to near room temperature at a desired temperature drop rate.

  In addition, after moving the crucible 14 etc. below the lower end part of the heater 11, you may comprise so that the crucible 14 etc. may be moved to a horizontal direction etc. further as needed.

  A method for suppressing the radiant heat from the melt from reaching the grown RIG as compared with the case where the surface of the melt and the grown RIG are directly opposed to each other is shown in FIGS. It is not limited to the form shown in b). Other configuration examples will be described with reference to FIGS. 2A, 2B, 3A, and 3B. 2 (a), FIG. 2 (b), FIG. 3 (a), and FIG. 3 (b), the same members as those in FIG. 1 (a) and FIG. .

  The film forming apparatus 20 shown in FIG. 2A is configured such that the substrate support shaft 15 and the seed crystal substrate 16 can be moved above the upper end of the heater 11 instead of the crucible 14 or the like. The film forming apparatus 10 can be configured in the same manner as the film forming apparatus 10 in FIG.

  In the film forming apparatus 20 shown in FIG. 2A, the substrate support shaft 15 can be moved upward along the block arrow 201 by a transport mechanism (not shown) after the growth process is completed. Thereby, the substrate support shaft 15 and the seed crystal substrate 16 on which the RIG attached to the substrate support shaft 15 is formed can be moved upward from the upper end portion of the heater 11. Then, the shielding plate 27 is moved along the block arrow 202, and as shown in FIG. 2B, the shielding plate 27 can be disposed between the melt 13 and the seed crystal substrate 16 on which the RIG is formed. .

  In addition, after moving the board | substrate support shaft 15 upwards rather than the upper end part of the heater 11, you may comprise so that the board | substrate support shaft 15 may be moved to a horizontal direction etc. further as needed.

  With the state shown in FIG. 2B, the radiant heat from the melt 13 is shielded by the shielding plate 27 and can be configured not to reach the seed crystal substrate 16 on which the RIG is formed. For this reason, it can suppress that the radiant heat from the melt 13 reaches | attains the grown RIG rather than the case where it arrange | positions so that the surface of the melt 13 and the grown RIG may face directly.

  In FIG. 2B, a heater may be provided around the seed crystal substrate 16 as necessary to control the temperature lowering rate.

  1 (a), 1 (b), 2 (a), and 2 (b) show a method of shielding radiant heat from the melt using a shielding object. Is not particularly limited, and for example, a heat insulating material, a reflection plate, or the like can be suitably used.

  The performance required for the shield is not particularly limited. For example, it is preferable that the thermal conductivity at 300 ° C. is 150 W / m · k or less and the melting point is 1000 ° C. or more. This is because when the thermal conductivity of the shielding object at 300 ° C. exceeds 150 W / m · k, the rear surface (RIG side) of the shielding object becomes high temperature, and radiation heat from the shielding object to the RIG is generated, thereby heating the RIG. Because there is a fear. Moreover, it is because there exists a possibility that it may melt | dissolve and deform | transform by the heat | fever from a melt etc., when it arrange | positions between melt and RIG as melting | fusing point is less than 1000 degreeC.

  Materials that satisfy the above conditions include Fe, Ni, Cr, stainless steel made using these, and Mo, W, Pt, etc. used in refractory crystal growth furnaces and crucible materials. Can be mentioned. For this reason, it is preferable that the material of the shield includes one or more selected from Fe, Ni, Cr, stainless steel, Mo, W, and Pt.

  When using a shield to suppress radiant heat from the melt to the RIG, between the grown bismuth-substituted rare earth iron garnet crystal film and the melt after the growth process and until the cooling process is completed. It is preferable to arrange a shield. By suppressing the radiant heat from the melt from reaching the RIG until the cooling process is completed after the completion of the growing process, it is possible to more reliably suppress the occurrence of cracks and cracks in the grown RIG. Because it can.

  Other forms will be described with reference to FIGS. 3A and 3B.

  In the film forming apparatus 30 shown in FIG. 3A, the shielding plate as a shielding object is not provided, and the movement form of the crucible 14 and the like is changed, and the film forming apparatus 30 shown in FIGS. The film forming apparatus 10 shown in FIG.

  In the film forming apparatus 30 shown in FIG. 3A, after the growth process is completed, the crucible 14 containing the melt 13 and the crucible base 12 are moved along, for example, a block arrow 301 by a transport mechanism (not shown). it can. Thereby, as shown in FIG. 3B, the crucible 14 containing the melt 13 can be moved to a position shifted from the lower side of the seed crystal substrate 16 on which the RIG is formed. The crucible 14 containing the melt 13 is moved to the position shown in FIG. 3B, so that the surface of the melt 13 and the grown RIG are arranged so as to face each other directly. It is possible to suppress the radiant heat from reaching the grown RIG.

  As shown in FIG. 3B, after the movement, the crucible 14 containing the melt 13 is located below the lower end of the heater 11 and in a region outside the region 31 surrounded by the heater 11. Preferably it is located.

  3A and 3B show an example in which the crucible 14 containing the melt 13 and the crucible base 12 are moved, the present invention is not limited to such a form. For example, the substrate support shaft 15 and the seed crystal substrate 16 on which the RIG is grown attached to the substrate support shaft 15 can be moved. In this case, the substrate support shaft 15 and the seed crystal substrate 16 on which the RIG is grown can be moved to a position above the upper end of the heater 11 and deviated from the position directly above the melt 13. In particular, it is preferably located above the upper end of the heater 11 and outside the region 31 surrounded by the heater 11.

  After the cooling step is completed, the RIG and the nonmagnetic garnet substrate as the seed crystal substrate can be taken out from the film forming apparatus.

  According to the RIG manufacturing method of the present embodiment described above, after the RIG is formed on the seed crystal substrate in the growing process, it is possible to prevent the RIG from being cracked or cracked in the cooling process. For this reason, the manufacturing yield of RIG can be improved.

Specific examples and comparative examples will be described below, but the present invention is not limited to these examples.
[Example 1]
Using the film forming apparatus 10 shown in FIGS. 1A and 1B, RIG was formed by the following procedure.

First, as raw materials, Nd ₂ O ₃ 39.27 g, Gd ₂ O ₃ 46.53 g, Fe ₂ O ₃ 313.08 g, Bi ₂ O ₃ 4304.44 g, PbO 721.65 g, B ₂ O ₃ was measured by 75.03 g and CaO by 4.40 g. Then, the weighed raw materials were put in a platinum crucible 14 and placed on the crucible base 12.

  Next, heating was performed by the heater 11, and the raw material filled in the crucible 14 was melted at 1000 ° C. to form a melt. In order to obtain a uniform composition of the melt, a propeller-like stirrer (not shown) disposed in the crucible 14 was sufficiently stirred and mixed by rotating in one direction at 100 rpm / min.

  Next, in order to grow RIG by the liquid phase epitaxial method, the temperature of the melt was lowered to a growth temperature of 825 ° C.

Thereafter, the nonmagnetic garnet substrate as the seed crystal substrate 16 is lowered while being rotated at 60 rpm by the substrate support shaft 15, and only one surface of the seed crystal substrate 16 facing the melt 13 is brought into contact with the melt 13. RIG formation started. As the nonmagnetic garnet substrate, a Gd ₃ (ScGa) ₅ O ₁₂ substrate having a diameter of 2 inches, a thickness of 400 μm, and a lattice constant of 1.256 nm is used.

  Then, while rotating the seed crystal substrate 16, only one surface of the seed crystal substrate 16 was kept in contact with the melt 13, and RIG was epitaxially grown until the RIG thickness became 250 μm (growth step). .

  After completion of the growth process, the substrate support shaft 15 was raised upward, and the seed crystal substrate 16 was separated from the melt 13. Then, after the crucible 14 containing the melt 13 and the crucible base 12 are moved downward along the block arrow 101 by a conveying means (not shown), the shielding plate 17 which is a shield is moved along the block arrow 102. Then, as shown in FIG. 1B, a shielding plate 17 was disposed between the seed crystal substrate 16 and the melt 13. This cut off the radiant heat from the melt 13 to the RIG.

  In addition, as the shielding plate 17, a shielding plate made of SUS304 is used, and the melting point is 1400 ° C., and the thermal conductivity at 300 ° C. is 16.7 W / m · k.

  And after installing the shielding board 17 as mentioned above, the output of the heater 11 was controlled and it cooled with the temperature-fall rate of 22.7 degrees C / hr. After cooling, the seed crystal substrate on which the RIG was formed was taken out from the furnace and evaluated.

  In the evaluation, RIG on the seed crystal substrate was observed visually and using a stereomicroscope to confirm the number of cracks. In addition, since the crack means the state which the crack progressed and the cut line entered into the thickness direction of RIG, the number of cracks is also included in the number of the cracks evaluated here.

  Also, the RIG is cut with a dicing saw together with the seed crystal substrate so that there are nine 11 mm squares, and those with corner chipping deformation due to cracks occurring in the RIG are considered defective, and those without corner chipping are non-defective. The number was determined as the number of good products. Moreover, the ratio of the number of non-defective products was calculated as the non-defective product yield.

  In addition, when the yield of good products is high, it means that the number of cracks and / or the length of cracks is short, and the occurrence of cracks can be suppressed compared to the case where the yield of good products is low. I can say that.

The results are shown in Table 1.
[Examples 2 to 8]
RIG was formed and cooled in the same manner as in Example 1 except that the cooling rate in the cooling step was changed to the rate shown in Table 1.

The evaluation results are shown in Table 1.
[Comparative Examples 1 to 5]
The RIG was formed and cooled in the same manner as in Example 1 except for the following two points.

  The point which made the cooling rate in a cooling process the value shown in Table 1.

  After the growth process, the melt 13 was separated from the seed crystal substrate 16 on which the RIG was formed. However, the crucible 14 containing the melt 13 and the crucible base 12 were not moved, and the melt 13 was not moved. And the cooling step was performed without arranging the shielding plate 17 between the seed crystal substrate on which the RIG was formed. In this case, the surface of the melt 13 and the grown RIG are arranged so as to face each other directly.

The evaluation results are shown in Table 1.
[Comparative Examples 6 to 8]
RIG was formed and cooled in the same manner as in Example 1 except that the cooling rate in the cooling step was the value shown in Table 1.

  The evaluation results are shown in Table 1.

表１の結果から、融液の表面と、育成したビスマス置換型希土類鉄ガーネット結晶膜とが直接対向するように配置した場合よりも、融液からの輻射熱が、育成したビスマス置換型希土類鉄ガーネット結晶膜に到達することを抑制し、かつ冷却速度を２００℃／ｈｒ以下にした実施例１〜実施例８では、上記条件のうち少なくとも一方を満たさない比較例１〜比較例８と比較して、クラックの発生が比較的少ないことが確認できた。

From the results of Table 1, the radiant heat from the melt is higher than that in the case where the melt surface and the grown bismuth-substituted rare earth iron garnet crystal film are directly opposed to each other. In Example 1 to Example 8 in which reaching to the crystal film is suppressed and the cooling rate is set to 200 ° C./hr or less, compared with Comparative Examples 1 to 8 that do not satisfy at least one of the above conditions. It was confirmed that the occurrence of cracks was relatively small.

  In Examples 1 to 8, it was confirmed that the yield of non-defective products was 50% or more. In contrast, in Comparative Examples 1 to 8, the yield of non-defective products was 44.4% or less.

  From the above results, in Examples 1 to 8, it can be confirmed that the number of cracks and / or the length of cracks can be suppressed as compared with Comparative Examples 1 to 8, and the occurrence of cracks can be confirmed. It was confirmed that it was suppressed.

  Among Examples 1 to 8, in particular, Examples 5 and 6 having a cooling rate in the range of 50 ° C./hr to 80 ° C./hr had a good product yield of 88.9%.

  For Comparative Examples 3 and 4, except that no shield was used, the same conditions as in Examples 5 and 6 were obtained, but cracks were caused by the radiant heat from the melt. The yield of good products was as low as 33.3%. From this, it was confirmed that radiant heat had an effect on the occurrence of cracks and cracks.

13 Melt 16 Seed crystal substrate (Non-magnetic garnet substrate)

Claims (6)

A nonmagnetic garnet substrate is brought into contact with a melt, and a bismuth-substituted rare earth iron garnet crystal film is grown on the nonmagnetic garnet substrate by a liquid phase epitaxial growth method,
After the growth step of growing the bismuth-substituted rare earth iron garnet crystal film, the cooling step of cooling from the growth temperature to room temperature,
In the cooling step,
The temperature drop rate is 200.0 ° C./hr or less,
And after the completion of the growth step, the crucible containing the melt is moved downward, and then a shielding plate is inserted between the grown bismuth-substituted rare earth iron garnet crystal film and the melt. , the surface of the melt, and the bismuth-substituted rare earth iron garnet crystal film grown than when placed so as to face directly, radiant heat from the melt, the bismuth and grown-substituted rare earth iron garnet crystal A method of manufacturing a bismuth-substituted rare earth iron garnet crystal film configured to suppress reaching the film.   2. The method for producing a bismuth-substituted rare earth iron garnet crystal film according to claim 1, wherein the cooling rate is 50 ° C./hr or more and 80 ° C./hr or less. After the completion of the growing process, until the cooling process is completed,
Said Bi-substituted rare earth iron garnet crystal film grown, the melt and the method of manufacturing a bismuth-substituted rare earth iron garnet crystal film according to claim 1 or 2, arranging the shielding plate between. The shielding plate is
The method for producing a bismuth-substituted rare earth iron garnet crystal film according to claim 3, wherein the thermal conductivity at 300 ° C is 150 W / m · k or less and the melting point is 1000 ° C or more. Development composition of the bismuth-substituted rare earth iron garnet crystal film general to formula _{Gd 3-x-y Bi x} R y Fe 5 O 12 ( where, R represents La, Ce, Pr, 1 or more selected from Nd The manufacturing method of the bismuth substitution type rare earth iron garnet crystal film as described in any one of Claims 1-4 which consists of rare earth elements and is shown by 0 <x, 0 <y). The method for producing a bismuth-substituted rare earth iron garnet crystal film according to claim 1, wherein the nonmagnetic garnet substrate is a Gd ₃ (ScGa) ₅ O ₁₂ substrate.

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