JP6500807B2 - Growth method of CaMgZr substituted gadolinium gallium garnet (SGGG) single crystal - Google Patents

Growth method of CaMgZr substituted gadolinium gallium garnet (SGGG) single crystal Download PDF

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JP6500807B2
JP6500807B2 JP2016034476A JP2016034476A JP6500807B2 JP 6500807 B2 JP6500807 B2 JP 6500807B2 JP 2016034476 A JP2016034476 A JP 2016034476A JP 2016034476 A JP2016034476 A JP 2016034476A JP 6500807 B2 JP6500807 B2 JP 6500807B2
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飯田　潤二
潤二 飯田
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Sumitomo Metal Mining Co Ltd
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本発明は、ＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法に関し、より詳しくは、チョクラルスキー（ＣＺ：Ｃｚｏｃｈｒａｌｓｋｉ）法により長尺のＳＧＧＧ単結晶を育成したとき、その結晶トップ部と結晶ボトム部間における格子定数差を極めて少なくしうるＳＧＧＧ単結晶の育成方法に関するものである。   The present invention relates to a method of growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal, and more particularly, when a long SGGG single crystal is grown by the Czochralski (CZ) method, the crystal top The present invention relates to a method of growing an SGGG single crystal capable of extremely reducing the difference in lattice constant between the portion and the bottom portion of the crystal.

光アイソレータは、磁界を印加することにより入射光の偏光面を回転させるファラデー回転子を有しており、近年、光アイソレータは、光通信の分野だけでなくファイバーレーザー加工機にも使用されるようになってきている。   The optical isolator has a Faraday rotator that rotates the polarization plane of incident light by applying a magnetic field, and in recent years, the optical isolator is likely to be used not only in the field of optical communication but also in fiber laser processing machines It has become

このような光アイソレータに使用されるファラデー回転子の材料として、ＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（Ｓｕｂｓｔｉｔｕｔｅｄ Ｇｄ５Ｇａ３Ｏ１２：ＳＧＧＧ）単結晶を基板（非磁性ガーネット単結晶基板）とし、該ＳＧＧＧ基板上に液相エピタキシャル（Ｌｉｑｕｉｄ Ｐｈａｓｅ Ｅｐｉｔａｘｙ；ＬＰＥ）成長させて得られるビスマス置換希土類鉄ガーネット単結晶膜（ＲＩＧ：Ｒａｒｅ−ｅａｒｔｈ ｉｒｏｎ ｇａｒｎｅｔ）が知られているが（特許文献１および特許文献２参照）、この膜は近赤外領域で高い透過率を有しかつ大きなファラデー効果を示す優れた材料である。 As a material of a Faraday rotator used for such an optical isolator, a CaMgZr-substituted gadolinium gallium garnet (Substituted Gd 5 Ga 3 O 12 : SGGG) single crystal is used as a substrate (nonmagnetic garnet single crystal substrate), A bismuth-substituted rare earth iron garnet single crystal film (RIG: Rare-earth iron garnet) obtained by liquid phase epitaxial (Liquid Phase Epitaxy; LPE) growth on an SGGG substrate is known (Patent Document 1 and Patent Document 2). Reference), this film is an excellent material having high transmittance in the near infrared region and exhibiting a large Faraday effect.

尚、非磁性ガーネット単結晶基板としては、該単結晶の育成方向における結晶方位が＜１１１＞、すなわち、非磁性ガーネット単結晶基板の（１１１）面上にＬＰＥ法により酸化物ガーネット単結晶膜が育成されている基板が利用されている（特許文献３参照）。ここには、チョクラルスキー法等の回転引上げ法により、予め混合したＧｄ２Ｏ３、Ｇａ２Ｏ３、ＭｇＯ、ＺｒＯ２、ＣａＣＯ３を坩堝内に所定量仕込み、高周波炉で加熱溶融して原料融液を得た後、坩堝内の原料融液に種結晶を接触させ、種結晶を回転させながら該種結晶を徐々に引き上げてＳＧＧＧ単結晶を育成することが記載されている。 As the nonmagnetic garnet single crystal substrate, the crystal orientation in the growth direction of the single crystal is <111>, that is, the oxide garnet single crystal film is formed by the LPE method on the (111) plane of the nonmagnetic garnet single crystal substrate. A substrate being grown is used (see Patent Document 3). Here, a predetermined amount of Gd 2 O 3 , Ga 2 O 3 , MgO, ZrO 2 , CaCO 3 mixed in advance is charged into a crucible by a rotational pulling method such as the Czochralski method, and heated and melted in a high frequency furnace. It is described that after the raw material melt is obtained, the seed crystal is brought into contact with the raw material melt in the crucible and the seed crystal is gradually pulled up while rotating the seed crystal to grow an SGGG single crystal.

前記の特許文献１〜２には、格子定数が１．２４９２〜１．２５１０ｎｍ、または１．２５０１〜１．２５１０ｎｍのＳＧＧＧ基板が記載されているが、ビスマス置換希土類鉄ガーネット（ＲＩＧ）単結晶膜をＳＧＧＧ基板上に、液相エピタキシャル（ＬＰＥ）成長法を用い、３００〜５００μｍ程度の厚さに安定的に育成させるには、基板の格子定数をＲＩＧ単結晶膜に整合させる必要がある。
基板とＲＩＧ単結晶膜との格子定数差が大き過ぎる場合、ＲＩＧ単結晶膜が、格子定数の異なるＳＧＧＧ基板の格子定数に整合するように、所望の組成とは異なる組成で成長してしまい、ＲＩＧ単結晶膜の特性が変化してしまうからである。 Patent documents 1 and 2 described above describe SGGG substrates having a lattice constant of 1.2492-1.250 nm or 1.2501-1.510 nm, but bismuth-substituted rare earth iron garnet (RIG) single crystal films In order to stably grow the SGGG substrate on the SGGG substrate to a thickness of about 300 to 500 μm using liquid phase epitaxial (LPE) growth, it is necessary to match the lattice constant of the substrate to the RIG single crystal film.
If the lattice constant difference between the substrate and the RIG single crystal film is too large, the RIG single crystal film grows with a composition different from the desired composition so as to match the lattice constant of the SGGG substrate having different lattice constants. This is because the characteristics of the RIG single crystal film change.

そこで、ＲＩＧ単結晶膜と格子定数を整合させるため、基板として使用されるＳＧＧＧは、格子定数１．２３８３ｎｍのガドリニウム・ガリウム・ガーネット単結晶（ＧＧＧ：Ｇｄ３Ｇａ５Ｏ１２）に、カルシウム（Ｃａ）、マグネシウム（Ｍｇ）、ジルコニウム（Ｚｒ）を添加して１．２４９５０〜１．２４９８５ｎｍの格子定数を得ている。 Therefore, in order to match the lattice constant with the RIG single crystal film, SGGG used as a substrate is calcium (Ca) in gadolinium gallium garnet single crystal (GGG: Gd 3 Ga 5 O 12 ) with a lattice constant of 1.2383 nm. ), Magnesium (Mg) and zirconium (Zr) are added to obtain a lattice constant of 1.24950 to 1.24985 nm.

しかし、ＳＧＧＧは一致溶融結晶ではなく、各添加元素（Ｃａ、Ｍｇ、Ｚｒ）は僅かながら偏析を示すと共に、各添加元素の濃度に依存して格子定数が変化するため、同一結晶において結晶育成初期のトップ部と結晶育成後期のボトム部とでは格子定数が異なり、ボトム部の格子定数がトップ部に比べて大きくなるという問題があった。
そこで、結晶を育成する際は、トップ部の格子定数が１．２４９５０〜１．２４９６０ｎｍの範囲に入るようにし、ボトム部においても格子定数が１．２４９８５ｎｍを超えないように工夫する必要があった。 However, SGGG is not a congruent melt crystal, and each additional element (Ca, Mg, Zr) shows segregation while slightly, and the lattice constant changes depending on the concentration of each additional element, so the crystal growth initial stage in the same crystal The lattice constant is different between the top of the crystal and the bottom of the crystal growth stage, and the lattice constant of the bottom is larger than that of the top.
Therefore, when growing a crystal, it was necessary to make the lattice constant of the top part fall within the range of 1.24950 to 1.24960 nm and devise that the lattice constant does not exceed 1.24985 nm also at the bottom part .

加えて、結晶育成終了後には、坩堝内に残った原料を再利用し、これに前回の結晶育成により減った分の原料を追加して、次回の結晶育成を開始するが、ＳＧＧＧは一致溶融結晶ではないために、育成した結晶の正確な平均組成を把握することが難しく、結晶育成回数を重ねるにつれて、トップ部とボトム部の格子定数差がさらに大きくなる傾向があった。   In addition, after completion of crystal growth, the raw material remaining in the crucible is reused, and the material reduced by the previous crystal growth is added to this to start the next crystal growth, but SGGG is consistently melted. Since it is not a crystal, it is difficult to grasp the accurate average composition of the grown crystal, and as the number of times of crystal growth is increased, the difference in lattice constant between the top portion and the bottom portion tends to further increase.

尚、上記ＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶は、（Ｇｄ３−ｘＣａｘ）（Ｇａ５−ｘ−２ｙＭｇｙＺｒｘ＋ｙ）Ｏ１２（ここで０＜ｘ＜３、０＜ｙ＜１）、あるいは（ＧｄＣａ）３（ＧａＭｇＺｒ）５Ｏ１２、（ＧｄＣａＧａＭｇＺｒ）８Ｏ１２等の組成式で表わされる。 Incidentally, the CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal, (Gd 3-x Ca x ) (Ga 5-x-2y Mg y Zr x + y) O 12 ( where 0 <x <3, 0 It is represented by a composition formula such as <y <1), (GdCa) 3 (GaMgZr) 5 O 12 , (GdCaGaMgZr) 8 O 12 or the like.

上述のように、チョクラルスキー法により育成されるＳＧＧＧ単結晶においては、原料融液から単結晶化する際に添加元素（Ｃａ、Ｍｇ、Ｚｒ）が偏析するため、育成初期のトップ部と育成後期のボトム部とで格子定数が同じにならない。   As described above, in the SGGG single crystal grown by the Czochralski method, the additional element (Ca, Mg, Zr) is segregated when single crystallizing from the raw material melt, so the top portion and the growth in the initial stage of growth The lattice constant does not become the same in the late bottom part.

結晶育成の経済的な側面からは、一回の育成で得られる結晶をできるだけ長尺化することが望ましいが、格子定数が変化するためトップ部では所望の格子定数だったとしてもボトム部では格子定数が所望の範囲を超えてしまい、長尺化を妨げていた。   From the economic aspect of crystal growth, it is desirable to lengthen the crystal obtained in one growth as much as possible, but the lattice constant changes, so that the lattice constant at the bottom even if the desired lattice constant at the top. The constant exceeds the desired range, which hinders the lengthening.

特開２００３−２３８２９４号公報JP 2003-238294 A 特開２００３−２３８２９５号公報JP 2003-238295 A 特開２０００−８９１６５号公報JP 2000-89165 A

本発明の目的は、このような従来技術の問題点に鑑み、チョクラルスキー法により育成されたＳＧＧＧ単結晶のトップ部とボトム部との格子定数差が極めて少ないＳＧＧＧ単結晶が得られる育成方法を提供することにある。   An object of the present invention is, in view of such problems of the prior art, a growth method by which an SGGG single crystal having an extremely small difference in lattice constant between the top portion and the bottom portion of the SGGG single crystal grown by the Czochralski method is obtained. To provide.

本発明者は、上記課題を解決するため鋭意研究を行った結果、組成式（ＧｄＣａＧａＭｇＺｒ）８Ｏ１２で示される原料融液中のカルシウムとマグネシウムの原子比Ｃａ／Ｍｇと、ガリウム量、ジルコニウム量とが特定範囲となるように、原料を混合し加熱溶融することで、トップ部とボトム部との格子定数差を小さく制御できることを見出して本発明を完成するに至った。 The inventors of the present invention conducted intensive studies to solve the above problems, and as a result, the atomic ratio Ca / Mg of calcium and magnesium in the raw material melt represented by the composition formula (GdCaGaMgZr) 8 O 12 , the amount of gallium, and the amount of zirconium The inventors have found that the difference in lattice constant between the top portion and the bottom portion can be controlled to be small by mixing the materials and heating and melting so that the ratio is within a specific range, and the present invention has been completed.

すなわち、本発明の第１の発明によれば、Ｇｄ、Ｃａ、Ｇａ、Ｍｇ、Ｚｒと酸素からなる原料融液表面に種結晶を接触させて回転させながら引き上げるチョクラルスキー（ＣＺ：Ｃｚｏｃｈｒａｌｓｋｉ）法によりＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶を育成する方法において、原料は、育成開始時の原料融液が下記組成式（１）で示される組成となる量を用いて、長尺の直胴部を有する単結晶を育成することを特徴とするＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法が提供される。
（ＧｄａＣａｂＧａｃＭｇｄＺｒｅ）Ｏ１２ （１）
［但し、組成式（１）中において、３ａ＋２ｂ＋３ｃ＋２ｄ＋４ｅ＝２４、ｂ＋ｄ＝ｅ、１．２５≦ｂ／ｄ≦１．３５、４．０１４≦ｃ≦４．０３４、０．６２９≦ｅ≦０．６３６である。］ That is, according to the first invention of the present invention, the Czochralski (CZ: Czochralski) method brings a seed crystal into contact with the surface of a raw material melt consisting of Gd, Ca, Ga, Mg, Zr and oxygen and pulls it while rotating it. In the method of growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal by the above method, the raw material is a long material using an amount such that the raw material melt at the start of the growth has a composition represented by the following composition formula (1) There is provided a method of growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal, characterized in that a single crystal having a straight body portion is grown.
(Gd a Ca b Ga c Mg d Zr e ) O 12 (1)
[Wherein, in the composition formula (1), 3a + 2b + 3c + 2d + 4e = 24, b + d = e, 1.25 ≦ b / d ≦ 1.35, 4.014 ≦ c ≦ 4.034, 0.629 ≦ e ≦ 0.636 It is. ]

また、本発明の第２の発明によれば、第１の発明において、得られる単結晶は、１００ｍｍ以上の長尺の直胴部を有することを特徴とするＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法によって提供される。   Further, according to the second invention of the present invention, in the first invention, a single crystal obtained has a straight cylindrical portion having a length of 100 mm or more, and is characterized by comprising: CaMgZr-substituted gadolinium gallium garnet ( SGGG) Provided by a method of growing a single crystal.

また、本発明の第３の発明によれば、第１又は２の発明において、原料融液は、固化率がボトム部で３５％以上であることを特徴とするＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法によって提供される。   Further, according to the third invention of the present invention, in the first or second invention, the raw material melt has a solidification rate of 35% or more at the bottom portion, and the CaMgZr-substituted gadolinium gallium garnet is characterized. (SGGG) Provided by a method of growing a single crystal.

さらに、本発明の第４の発明によれば、第１〜３のいずれかの発明において、得られる単結晶は、結晶ボトム部と結晶トップ部における格子定数の差が０．０００２ｎｍ以下であることを特徴とするＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法によって提供される。   Furthermore, according to the fourth invention of the present invention, in any of the first to third inventions, the single crystal obtained has a difference in lattice constant between the crystal bottom portion and the crystal top portion of 0.0002 nm or less A method of growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal characterized by

本発明に係るＳＧＧＧ単結晶の育成方法によれば、単結晶インゴットのトップ部から得られたＳＧＧＧ基板とボトム部から得られたＳＧＧＧ基板における格子定数差が極めて小さいため、結晶を長尺化しても、基板の格子定数を所望の範囲に収めることができる。
また、得られたＳＧＧＧ基板は、基板の格子定数が所望の組成のＲＩＧ単結晶膜の格子定数と整合しているために、所望の組成のＲＩＧ単結晶膜を成長させることができる。 According to the SGGG single crystal growth method of the present invention, the difference in lattice constant between the SGGG substrate obtained from the top portion of the single crystal ingot and the SGGG substrate obtained from the bottom portion is extremely small. Also, the lattice constant of the substrate can be within the desired range.
Further, in the obtained SGGG substrate, since the lattice constant of the substrate matches the lattice constant of the RIG single crystal film of the desired composition, the RIG single crystal film of the desired composition can be grown.

本発明に係るＳＧＧＧ単結晶の育成方法に用いられる製造装置の概略構成を模式的に示す説明図である。It is explanatory drawing which shows typically schematic structure of the manufacturing apparatus used for the growth method of the SGGG single crystal which concerns on this invention. 本発明に係るＳＧＧＧ単結晶の外観であり、直胴部におけるトップ部とボトム部を示す説明図である。It is an external appearance of the SGGG single crystal which concerns on this invention, and is explanatory drawing which shows the top part and bottom part in a straight trunk | drum. ＳＧＧＧ単結晶を構成するＣａ／Ｍｇ原子比を変化させたときの、トップ部とボトム部の格子定数差を一例として示すグラフである。It is a graph which shows as an example the lattice constant difference of the top part and the bottom part when changing the Ca / Mg atomic ratio which constitutes SGGG single crystal.

以下、本発明のＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法の実施の形態について、図面を参照して詳細に説明する。   Hereinafter, an embodiment of a method for growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal of the present invention will be described in detail with reference to the drawings.

（１）ＳＧＧＧ単結晶を育成する製造装置
図１は、本発明に係るＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法に用いられる製造装置の概略構成を示す説明図である。 (1) Manufacturing Apparatus for Growing SGGG Single Crystal FIG. 1 is an explanatory view showing a schematic configuration of a manufacturing apparatus used for a method for growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal according to the present invention.

この製造装置は、公知のチョクラルスキー法によりＳＧＧＧ単結晶を育成する育成炉１を備えている。育成炉１の構造を簡単に説明すると、育成炉１は、筒状のチャンバー２と、このチャンバー２の内側に設置された高周波コイル１０と、この高周波コイル１０の内側に配置された断熱材３およびイリジウム製坩堝８を有している。   This manufacturing apparatus includes a growth furnace 1 for growing an SGGG single crystal by a known Czochralski method. The structure of the growth furnace 1 will be briefly described. The growth furnace 1 includes a cylindrical chamber 2, a high frequency coil 10 disposed inside the chamber 2, and a heat insulating material 3 disposed inside the high frequency coil 10. And an iridium crucible 8.

また、上記育成炉１には開口部（図示せず）が２箇所設けられており、これら開口部を介して不活性ガス、好適には窒素ガスが給排され、結晶育成時のチャンバー２内は不活性ガスで満たされる。尚、図示しないが、育成炉１内には、上記坩堝８底部の下側に温度を計測する温度計（熱電対）が設置されている。   Further, the growing furnace 1 is provided with two openings (not shown), through which inert gas, preferably nitrogen gas is supplied and discharged, and the inside of the chamber 2 at the time of crystal growth Is filled with inert gas. Although not shown, a thermometer (thermocouple) for measuring the temperature is provided in the growth furnace 1 below the bottom of the crucible 8.

また、上記高周波コイル１０は銅管で構成され、制御部（図示せず）を通じ投入電力が制御されて坩堝８が高周波加熱されると共に温度調節がなされる。また、上記チャンバー２の内側で高周波コイル１０内には断熱材３が配置されており、複数の断熱材３により囲まれた雰囲気によりホットゾーン５が形成されている。   Further, the high frequency coil 10 is formed of a copper pipe, and the input power is controlled through a control unit (not shown) to heat the crucible 8 at high frequency and to control the temperature. Further, a heat insulating material 3 is disposed inside the high frequency coil 10 inside the chamber 2, and a hot zone 5 is formed by an atmosphere surrounded by the plurality of heat insulating materials 3.

上記ホットゾーン５の上下方向における温度勾配は高周波コイル１０への投入電力量を制御することによって変化させることができ、かつ、断熱材３の形状と構成（材質）によっても広範囲に変化させることができる。更に、高周波コイル１０の坩堝８に対する相対位置を調整することによりホットゾーン５の温度勾配を微調整することができる。尚、上記断熱材３は、高融点の耐火物により構成されている。   The temperature gradient in the vertical direction of the hot zone 5 can be changed by controlling the amount of input power to the high frequency coil 10, and can be changed widely depending on the shape and the configuration (material) of the heat insulating material 3 it can. Furthermore, the temperature gradient of the hot zone 5 can be finely adjusted by adjusting the relative position of the high frequency coil 10 to the crucible 8. The heat insulating material 3 is made of refractory having a high melting point.

また、上記坩堝８はカップ状に形成され、その底部が断熱材３上に配置され、かつ断熱材３により保持されている。また、坩堝８の上方側には、種結晶６と成長したＳＧＧＧ単結晶を保持し、かつ引き上げるための引き上げ軸４が設置されており、引き上げ軸４は軸線を中心に回転させることができる。   Further, the crucible 8 is formed in a cup shape, the bottom of which is disposed on the heat insulating material 3, and is held by the heat insulating material 3. Further, on the upper side of the crucible 8, there is provided a pulling shaft 4 for holding and pulling up the seed crystal 6 and the grown SGGG single crystal, and the pulling shaft 4 can be rotated about its axis.

（２）原料と加熱溶融
そして、坩堝８内に原料を充填し、育成炉１のチャンバー２内に上記坩堝８を配置してから、高周波コイル１０により加熱して原料を融解させる。 (2) Raw Material and Heating and Melting Then, the raw material is filled in the crucible 8, and after the crucible 8 is placed in the chamber 2 of the growth furnace 1, it is heated by the high frequency coil 10 to melt the raw material.

本発明では、まず原料として純度９９．９９％の酸化ガドリニウム（Ｇｄ２Ｏ３）、炭酸カルシウム（ＣａＣＯ３）、酸化ガリウム（Ｇａ２Ｏ３）、酸化マグネシウム（ＭｇＯ）、酸化ジルコニウム（ＺｒＯ２）を秤量する。 In the present invention, first, gadolinium oxide (Gd 2 O 3 ), calcium carbonate (CaCO 3 ), gallium oxide (Ga 2 O 3 ), magnesium oxide (MgO), zirconium oxide (ZrO 2 ) having purity of 99.99% as a raw material Weigh

次に、上記原料を混合し、冷間等方圧加圧法により嵩密度を増加させた後、空気中、１５００〜１６００℃で仮焼し、炭酸カルシウムから炭酸ガスを除去したものを坩堝に充填する。   Next, the above raw materials are mixed, bulk density is increased by a cold isostatic pressing method, and then calcined in air at 1500 to 1600 ° C. to fill the crucible with carbon dioxide gas removed from calcium carbonate. Do.

図３にカルシウムとマグネシウムの原子比Ｃａ／Ｍｇを変化させた場合のＳＧＧＧ単結晶トップ部とボトム部の格子定数差（トップ部の格子定数−ボトム部の格子定数）の一例を示す。図３はトップ部とボトム部の原料融液の固化率［（結晶重量÷原料重量）×１００］がそれぞれ１５％、３５％の例であるが、ボトム部の固化率が３５％であれば、Ｃａ／Ｍｇ比が１．３付近で格子定数差がほぼゼロとなり、Ｃａ／Ｍｇ比を１．２５以上１．３５以下とすることで、トップ部とボトム部の格子定数差を０．００００２ｎｍ以内に抑えることが可能となる。   FIG. 3 shows an example of the difference in lattice constant between the SGGG single crystal top portion and the bottom portion (lattice constant of the top portion-lattice constant of the bottom portion) when the atomic ratio Ca / Mg of calcium and magnesium is changed. FIG. 3 shows an example in which the solidification ratio [(crystal weight / raw material weight) × 100] of the raw material melt at the top and the bottom is 15% and 35%, respectively, but if the solidification ratio at the bottom is 35% The lattice constant difference becomes almost zero when the Ca / Mg ratio is around 1.3, and the lattice constant difference between the top portion and the bottom portion is 0.00002 nm by setting the Ca / Mg ratio to not less than 1.25 and not more than 1.35. It becomes possible to control within.

しかし、１回の単結晶育成で得られる単結晶基板の枚数を増やすことが望ましく、そのためには、直胴部を長くし、固化率の大きな単結晶を育成すれば良いが、固化率を大きくすると、ＳＧＧＧが原料融液から単結晶化する際の添加元素（Ｃａ、Ｍｇ、Ｚｒ）の偏析の影響が顕著となり、例えＣａ／Ｍｇ比を１．２５以上１．３５以下としたとしてもトップ部とボトム部の格子定数差が大きく乖離するようになる。   However, it is desirable to increase the number of single crystal substrates obtained by single crystal growth once, and for this purpose, it is sufficient to lengthen the straight body portion and grow single crystals having a large solidification rate, but the solidification rate is large. Then, the influence of segregation of the additional elements (Ca, Mg, Zr) when SGGG single-crystallizes from the raw material melt becomes remarkable, and the top even though the Ca / Mg ratio is 1.25 or more and 1.35 or less. The difference in lattice constant between the part and the bottom part largely diverges.

そこで、Ｃａ／Ｍｇ比を１．２５以上１．３５以下とした上で、固化率が大きい、例えば４７％の単結晶を育成したとしても、トップ部の格子定数が１．２４９５０〜１．２４９６０ｎｍとなり、ボトム部においても格子定数が１．２４８５ｎｍを超えない原料融液が得られるようにするには、それ以外のＧｄ、Ｇａ、Ｚｒについても組成範囲を考慮すべきことになる。   Therefore, the lattice constant of the top portion is 1.24950 to 1.24960 nm even if a single crystal with a large solidification rate, for example 47%, is grown after setting the Ca / Mg ratio to not less than 1.25 and not more than 1.35. Thus, in order to obtain a raw material melt whose lattice constant does not exceed 1.2485 nm even at the bottom portion, the composition range should be considered for the other Gd, Ga, and Zr.

本出願人は、下記組成式（１）で示される原料融液において、ＣａとＭｇの含有量の和（ｂ＋ｄ）がＺｒの含有量（ｅ）と等しく、Ｇａの含有量（ｃ）が４．０１４以上４．０３４以下で、Ｚｒの含有量（ｅ）が０．６２９以上０．６３６以下とすれば良いことを実験的に求めることができた。   The applicant has found that the sum (b + d) of the contents of Ca and Mg is equal to the content (e) of Zr, and the content (c) of Ga is 4 in the raw material melt represented by the following composition formula (1) It was possible to experimentally determine that the content (e) of Zr should be 0.629 or more and 0.636 or less at 0.14 or more and 4.034 or less.

（ＧｄａＣａｂＧａｃＭｇｄＺｒｅ）Ｏ１２ （１）
なお、上記組成式においてチャージバランスを取るために、各金属元素の含有量に価数を掛けたものの和は２４でなければならない。 (Gd a Ca b Ga c Mg d Zr e ) O 12 (1)
In order to achieve charge balance in the above composition formula, the sum of the contents of the respective metal elements multiplied by the valence must be 24.

（３）単結晶の引き上げ、育成
上記組成範囲となるように混合された原料を加熱溶融した後、図１のように原料融液９に種結晶６を接触させて徐々に温度を降下させ、同時に引き上げ軸４を徐々に引き上げることにより種結晶６の下部側において原料融液９を順次結晶化させる。 (3) Pulling up and Growing Single Crystals After heating and melting the raw materials mixed to be in the above composition range, the seed crystal 6 is brought into contact with the raw material melt 9 as shown in FIG. At the same time, the material melt 9 is sequentially crystallized on the lower side of the seed crystal 6 by gradually pulling the pulling shaft 4.

そして、育成条件に従い高周波コイル１０への投入電力を調整し、所望とする直径のＳＧＧＧ単結晶７を育成する。図２は育成されたＳＧＧＧ単結晶７を示し、符号１１はＳＧＧＧ単結晶７の直胴部における結晶トップ部、符号１２はＳＧＧＧ単結晶７の直胴部における結晶ボトム部をそれぞれ示している。   Then, the input power to the high frequency coil 10 is adjusted in accordance with the growth conditions to grow the SGGG single crystal 7 having a desired diameter. FIG. 2 shows the grown SGGG single crystal 7. Reference numeral 11 denotes a crystal top portion in a straight barrel portion of the SGGG single crystal 7, and reference numeral 12 denotes a crystal bottom portion in a straight barrel portion of the SGGG single crystal 7.

尚、単結晶の育成方向における結晶方位が＜１１１＞である非磁性ガーネット単結晶基板が広く用いられているため、育成されるＳＧＧＧ単結晶７の育成方向における結晶方位は＜１１１＞であることが好ましい。   Since a nonmagnetic garnet single crystal substrate having a crystal orientation of <111> in the growth direction of the single crystal is widely used, the crystal orientation in the growth direction of the SGGG single crystal 7 to be grown is <111> Is preferred.

引き上げ軸４を徐々に引き上げ、ＳＧＧＧ単結晶の肩部を育成するとき、ファセット成長に伴う歪の発生を抑制するため、結晶回転速度を急激に上昇させ、融液中に強制対流を発生させて自然対流と競合状態を作り、前述した凸形状部を溶かす「界面反転操作」を行って、界面形状を凸から平坦にする。また、単結晶育成に係る一連の温度モニタは上記温度計（熱電対）により行われる。   When raising the pulling shaft 4 gradually and growing the shoulder of the SGGG single crystal, the crystal rotation speed is rapidly increased to generate forced convection in the melt in order to suppress the generation of strain accompanying facet growth. The interface shape is made to be flat from convex by performing “interface inversion operation” in which competition with natural convection is made and the above-mentioned convex shape portion is melted. Further, a series of temperature monitoring relating to single crystal growth is performed by the above-mentioned thermometer (thermocouple).

ところで、チョクラルスキー法によるＳＧＧＧ単結晶の直胴部における育成条件は、特に限定されず、従来の育成条件（原料融液の加熱条件、例えば加熱温度、雰囲気ガス、加熱時間、界面反転操作など、従来から採用されている自動制御による条件）によることができる。   By the way, the growth conditions in the straight body portion of the SGGG single crystal by the Czochralski method are not particularly limited, and the conventional growth conditions (heating conditions of the raw material melt, for example, heating temperature, atmosphere gas, heating time, interface inversion operation, etc. Can be based on the condition under automatic control adopted conventionally.

好ましいのは、この育成条件を維持したまま、結晶育成炉内の原料融液９表面から引き上げ方向１ｃｍまでの雰囲気における温度勾配を７〜１４℃／ｃｍとし、１ｃｍを越え引き上げ方向１０ｃｍまでの雰囲気における温度勾配を１９〜２３℃／ｃｍの範囲に維持することである。それと共に、ＳＧＧＧ単結晶の直胴部上端から０ｍｍ〜３０ｍｍまでの直胴部育成中、上記種結晶６の回転数を２２〜３０ｒｐｍ、特に２２〜２５ｒｐｍ内の一定値（例えば２２ｒｐｍ）に設定し、直胴部上端から３０ｍｍを越えた以降の直胴部育成中、上記一定値（例えば２２ｒｐｍ）から一定の比率で回転数を減少させて直胴部上端から８３ｍｍ直胴部が育成した時点における種結晶６の回転数が１８〜２１ｒｐｍ（例えば１８ｒｐｍ）となるように管理するのが好ましい。   Preferably, the temperature gradient in the atmosphere from the surface of the raw material melt 9 in the crystal growth furnace to 1 cm in the pulling direction is 7 to 14 ° C./cm while maintaining this growth condition, and the atmosphere for 1 cm to the pulling direction 10 cm. Temperature gradient in the range of 19-23.degree. C./cm. At the same time, during straight barrel growth from 0 mm to 30 mm from the upper end of the straight barrel portion of the SGGG single crystal, the number of rotations of the seed crystal 6 is set to a constant value within 22 to 30 rpm, particularly 22 to 25 rpm (for example 22 rpm). During growth of the straight body after exceeding 30 mm from the upper end of the straight body, the rotational speed is reduced at a constant ratio from the above constant value (for example, 22 rpm) and the straight body is grown 83 mm from the upper end of the straight body It is preferable to manage so that the rotation speed of the seed crystal 6 may be 18 to 21 rpm (for example, 18 rpm).

こうして育成されたＳＧＧＧ単結晶は、図２に示すように、種結晶１下部の肩部と直胴部７を有したものとなり、例えば直径が８０ｍｍ以上、かつ１００ｍｍ以上の長尺のＳＧＧＧ単結晶の直胴部を育成することができる。   As shown in FIG. 2, the SGGG single crystal grown in this manner has a shoulder at the lower portion of the seed crystal 1 and a straight barrel 7. For example, a long SGGG single crystal having a diameter of 80 mm or more and 100 mm or more. The straight torso can be nurtured.

（４）直胴部の切断と基板
その後、直胴部は、インゴットの肩部との境界、すなわち結晶トップ部で切断・分離される。 (4) Cutting of Straight Body Portion and Substrate Thereafter, the straight body portion is cut and separated at the boundary with the shoulder portion of the ingot, that is, at the crystal top portion.

そして、分離した単結晶育成後の外形形状を有する直胴部は、ＳＧＧＧ単結晶基板として薄く種結晶側から切り出される。このＳＧＧＧ単結晶基板の格子定数差がトップとボトムで０．０００２ｎｍ以内になっているので、円筒研削により外径を整えた後、基板状に切断し、研磨した上でＬＰＥ育成用の基板として供することができる。   Then, the separated straight body having the external shape after single crystal growth is thinly cut out from the seed crystal side as an SGGG single crystal substrate. Since the difference in lattice constant of this SGGG single crystal substrate is within 0.0002 nm at the top and bottom, after the outer diameter is adjusted by cylindrical grinding, it is cut into the shape of a substrate, polished and used as a substrate for LPE growth. It can be provided.

以下、本発明の実施例について比較例とともに具体的に説明するが、本発明はこれらの実施例によってのみ限定されるものではない。   Examples of the present invention will be specifically described below along with comparative examples, but the present invention is not limited to these examples.

なお、育成したＳＧＧＧ単結晶は、そのトップ部とボトム部の格子定数をエックス線回折装置（Ｐｈｉｌｉｐｓ社製 ＰＡＮａｌｙｔｉｃａｌ Ｘ’ｐｅｒｔ ＰＲＯ ＭＲＤ）を用いて測定した。   The lattice constants of the top and bottom portions of the grown SGGG single crystal were measured using an X-ray diffractometer (Panalytical X'pert PRO MRD manufactured by Philips).

［実施例１］
ＳＧＧＧ単結晶をチョクラルスキー法で育成するため、表１に示す通り、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．７１０：０．３５８：４．０２４：０．２７５：０．６３３、および、Ｃａ／Ｍｇ＝０．３５８／０．２７５＝１．３０となるように、原料として純度９９．９９％の酸化ガドリニウム（Ｇｄ２Ｏ３）、炭酸カルシウム（ＣａＣＯ３）、酸化ガリウム（Ｇａ２Ｏ３）、酸化マグネシウム（ＭｇＯ）、酸化ジルコニウム（ＺｒＯ２）を秤量した。
そして、この原料を混合し、冷間等方圧加圧法により嵩密度を増加させた後、空気中、１５００〜１６００℃で仮焼し、炭酸カルシウムから炭酸ガスを除去した。仮焼後の重量は１２．６ｋｇであった。 Example 1
As shown in Table 1, atomic ratio Gd: Ca: Ga: Mg: Zr = 2.710: 0.358: 4.024: 0.275: 0.633 in order to grow SGGG single crystal by the Czochralski method. Gadolinium oxide (Gd 2 O 3 ), calcium carbonate (CaCO 3 ), gallium oxide (Gd 2 O 3 ) having a purity of 99.99%, so that Ca / Mg = 0.358 / 0.275 = 1.30 Ga 2 O 3 ), magnesium oxide (MgO), and zirconium oxide (ZrO 2 ) were weighed.
Then, the raw materials were mixed, bulk density was increased by a cold isostatic pressure method, and then calcined in air at 1500 to 1600 ° C. to remove carbon dioxide gas from calcium carbonate. The weight after calcination was 12.6 kg.

育成装置には図１に示すような製造装置を用い、上記仮焼したものを直径１５０ｍｍ、高さ１５０ｍｍのイリジウム坩堝に充填し、チャンバーを閉めた後、高周波コイルに電力を投入して、１７５０℃まで加熱して、原料を融解させた。
続いて、結晶方位が＜１１１＞である棒状種結晶の先端を原料融液に浸け、原料融液表面から引き上げ方向１ｃｍまでの雰囲気における温度勾配が７℃／ｃｍ、また１ｃｍを越え引き上げ方向１０ｃｍまでの雰囲気における温度勾配が１９℃／ｃｍの条件でＳＧＧＧ単結晶を育成した。 As a growth apparatus, a manufacturing apparatus as shown in FIG. 1 is used, and the calcined material is filled into an iridium crucible having a diameter of 150 mm and a height of 150 mm, and after closing the chamber, power is supplied to a high frequency coil. The raw material was melted by heating to ° C.
Subsequently, the tip of a rod-shaped seed crystal having a crystal orientation of <111> is immersed in the raw material melt, and the temperature gradient in the atmosphere from the surface of the raw material melt to 1 cm in the pulling direction is 7 ° C./cm. The SGGG single crystal was grown under the conditions of a temperature gradient of 19 ° C./cm in an atmosphere up to

ここで、直胴部上端から０ｍｍ〜３０ｍｍまでの直胴部を育成する際には、種結晶の回転数を２２ｒｐｍに設定し、直胴部上端から３０ｍｍを越えた以降の直胴部を育成する際には、２２ｒｐｍから一定の比率で回転数を減少させて直胴部上端から８３ｍｍ直胴部が育成した時点での種結晶の回転数が１８ｒｐｍとなるように管理しながらＳＧＧＧ単結晶直胴部の育成を行い、直径８３ｍｍで直胴部長１００ｍｍのＳＧＧＧ単結晶（５．９ｋｇ）を育成した。
尚、実施例１に係るＳＧＧＧ単結晶の原料融液の固化率［（結晶重量÷原料重量）×１００］＝［（５．９ｋｇ÷１２．６ｋｇ）×１００］＝４６．８％である。 Here, when growing a straight barrel from 0 mm to 30 mm from the upper end of the straight barrel, the rotational speed of the seed crystal is set to 22 rpm, and a straight barrel after 30 mm from the upper end of the straight barrel is grown At the same time, the rotational speed is reduced at a constant rate from 22 rpm, and the SGGG single crystal direct crystal is controlled so that the rotational speed of the seed crystal becomes 18 rpm when the 83 mm straight body grows from the upper end of the straight body. The body was grown to grow SGGG single crystal (5.9 kg) having a diameter of 83 mm and a straight body length of 100 mm.
The solidification ratio of the raw material melt of SGGG single crystal according to Example 1 [(crystal weight / raw material weight) × 100] = [(5.9 kg × 12.6 kg) × 100] = 46.8%.

次に、育成されたＳＧＧＧ単結晶の直胴部における結晶トップ部（直胴部の上端）と結晶ボトム部（直胴部の下端）を切断し、かつ、両面研磨加工を施した後、上記エックス線回折装置を用いて、トップ部から得られたＳＧＧＧ単結晶基板とボトム部から得られたＳＧＧＧ単結晶基板の格子定数を測定した。
測定の結果、表２に示す通り、トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９５５ｎｍ、かつ、ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９７３ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００１８ｎｍであった。
その後、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させると、基板の格子定数とＲＩＧ単結晶膜との格子定数差が極めて小さいので、所望の組成のＲＩＧ単結晶膜を成長させることができる。 Next, the crystal top (upper end of the straight barrel) and the crystal bottom (lower end of the straight barrel) in the straight barrel of the grown SGGG single crystal are cut and subjected to double-side polishing, The lattice constants of the SGGG single crystal substrate obtained from the top and the SGGG single crystal substrate obtained from the bottom were measured using an X-ray diffractometer.
As a result of measurement, as shown in Table 2, the lattice constant of the SGGG single crystal substrate obtained from the top is 1.24955 nm, and the lattice constant of the SGGG single crystal substrate obtained from the bottom is 1.24973 nm, The difference in lattice constant between the bottom portion and the crystal top portion was 0.00018 nm.
Thereafter, when the RIG single crystal film is grown by the LPE method using this SGGG substrate, the difference between the lattice constant of the substrate and the lattice constant of the RIG single crystal film is extremely small, so the RIG single crystal film of the desired composition is grown. be able to.

［実施例２］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．７２８：０．３５０：４．０１４：０．２７９：０．６２９、および、Ｃａ／Ｍｇ＝０．３５０／０．２７９＝１．２５となるように秤量したこと以外は実施例１と同様にして、ＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９５７ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９７６ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００１９ｎｍであった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させると、基板の格子定数とＲＩＧ単結晶膜との格子定数差が極めて小さいので、所望の組成のＲＩＧ単結晶膜を成長させることができる。 Example 2
A raw material of SGGG single crystal is prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.728: 0.350: 4.014: 0.279: 0.629, and Ca / Mg = 0.350 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that weighing was performed so that .279 = 1.25.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top is 1.24957 nm, and the SGGG single crystal obtained from the crystal bottom The lattice constant of the substrate was 1.24976 nm, and the difference in lattice constant between the crystal bottom portion and the crystal top portion was 0.00019 nm.
Thereafter, when the RIG single crystal film is grown by the LPE method using this SGGG substrate in the same manner as in Example 1, the difference between the lattice constant of the substrate and the lattice constant of the RIG single crystal film is extremely small. RIG single crystal films can be grown.

［実施例３］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．７１４：０．３６５：４．０１４：０．２７１：０．６３６、および、Ｃａ／Ｍｇ＝０．３６５／０．２７１＝１．３５となるように秤量したこと以外は実施例１と同様にしてＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９６０ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９７９ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００１９ｎｍであった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させると、基板の格子定数とＲＩＧ単結晶膜との格子定数差が極めて小さいので、所望の組成のＲＩＧ単結晶膜を成長させることができる。 [Example 3]
A raw material of SGGG single crystal is prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.714: 0.365: 4.014: 0.271: 0.636, and Ca / Mg = 0.365 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that weighing was performed so that .271 = 1.35.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top portion is 1.24960 nm, and the SGGG single crystal obtained from the crystal bottom portion The lattice constant of the substrate was 1.24979 nm, and the difference in lattice constant between the crystal bottom portion and the crystal top portion was 0.00019 nm.
Thereafter, when the RIG single crystal film is grown by the LPE method using this SGGG substrate in the same manner as in Example 1, the difference between the lattice constant of the substrate and the lattice constant of the RIG single crystal film is extremely small. RIG single crystal films can be grown.

［実施例４］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．６９８：０．３５３：４．０３０：０．２８３：０．６３６、および、Ｃａ／Ｍｇ＝０．３５３／０．２８３＝１．２５となるように秤量したこと以外は実施例１と同様にしてＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９５４ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９７５ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００２１ｎｍであった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させると、基板の格子定数とＲＩＧ単結晶膜との格子定数差が極めて小さいので、所望の組成のＲＩＧ単結晶膜を成長させることができる。 Example 4
A raw material of SGGG single crystal is prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.698: 0.353: 4.030: 0.283: 0.636, and Ca / Mg = 0.353 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that the measurement was made to have .283 = 1.25.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top is 1.24954 nm, and the SGGG single crystal obtained from the crystal bottom The lattice constant of the substrate was 1.24975 nm, and the difference in lattice constant between the crystal bottom portion and the crystal top portion was 0.00021 nm.
Thereafter, when the RIG single crystal film is grown by the LPE method using this SGGG substrate in the same manner as in Example 1, the difference between the lattice constant of the substrate and the lattice constant of the RIG single crystal film is extremely small. RIG single crystal films can be grown.

［実施例５］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．６９６：０．３６５：４．０３４：０．２７０：０．６３５、および、Ｃａ／Ｍｇ＝０．３６５／０．２７０＝１．３５となるように秤量したこと以外は実施例１と同様にしてＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９５０ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９７０ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００２０ｎｍであった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させると、基板の格子定数とＲＩＧ単結晶膜との格子定数差が極めて小さいので、所望の組成のＲＩＧ単結晶膜を成長させることができる。 [Example 5]
A raw material of SGGG single crystal is prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.696: 0.365: 4.034: 0.270: 0.635, and Ca / Mg = 0.365 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that weighing was performed so that .270 = 1.35.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top portion is 1.24950 nm, and the SGGG single crystal obtained from the crystal bottom portion The lattice constant of the substrate was 1.24970 nm, and the difference in lattice constant between the crystal bottom portion and the crystal top portion was 0.00020 nm.
Thereafter, when the RIG single crystal film is grown by the LPE method using this SGGG substrate in the same manner as in Example 1, the difference between the lattice constant of the substrate and the lattice constant of the RIG single crystal film is extremely small. RIG single crystal films can be grown.

［比較例１］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．７２３：０．３５９：４．０１１：０．２７４：０．６３３、および、Ｃａ／Ｍｇ＝０．３５９／０．２７４＝１．３１となるように秤量したこと以外は実施例１と同様にしてＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９６４ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９８６ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００２２ｎｍであった。結晶ボトム部と結晶トップ部における格子定数の差は実施例に比べて大きくはなっていないが、トップ部の格子定数が１．２４９６０ｎｍを上回っているため、ボトム部において１．２４９８５ｎｍを超えてしまった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させたが、格子定数が１．２４９８５ｎｍを超えているので、この基板では所望の組成のＲＩＧ単結晶膜を成長させることができなかった。 Comparative Example 1
A raw material of SGGG single crystal is prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.723: 0.359: 4.011: 0.274: 0.633, and Ca / Mg = 0.359 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that weighing was performed so that .274 = 1.31.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top is 1.24964 nm, and the SGGG single crystal obtained from the crystal bottom The lattice constant of the substrate was 1.24986 nm, and the difference in lattice constant between the crystal bottom portion and the crystal top portion was 0.00022 nm. Although the difference in lattice constant between the crystal bottom portion and the crystal top portion is not large as compared with the example, since the lattice constant of the top portion exceeds 1.24960 nm, the bottom portion exceeds 1.24985 nm. The
After that, a RIG single crystal film was grown by LPE method using this SGGG substrate in the same manner as in Example 1. However, since the lattice constant exceeds 1.24985 nm, a RIG single crystal of a desired composition is used in this substrate. The film could not be grown.

［比較例２］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．６９８：０．３５８：４．０３６：０．２７５：０．６３３、および、Ｃａ／Ｍｇ＝０．３５８／０．２７５＝１．３０となるように秤量したこと以外は実施例１と同様にしてＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９４８ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９６９ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００２１ｎｍであった。結晶ボトム部と結晶トップ部における格子定数の差は実施例に比べて大きくはなっていないが、トップ部において１．２４９５０ｎｍを下回ってしまった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させたが、格子定数が１．２４９５０ｎｍを下回っているので、この基板では所望の組成のＲＩＧ単結晶膜を成長させることができなかった。実施例５に対して、有効な基板数が減少することになる。 Comparative Example 2
The raw materials of SGGG single crystal were prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.698: 0.358: 4.036: 0.275: 0.633, and Ca / Mg = 0.358 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that weighing was performed so that .275 = 1.30.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top is 1.24948 nm, and the SGGG single crystal obtained from the crystal bottom The lattice constant of the substrate was 1.24969 nm, and the difference in lattice constant between the crystal bottom portion and the crystal top portion was 0.00021 nm. Although the difference in lattice constant between the crystal bottom portion and the crystal top portion is not large as compared with the example, it falls below 1.24950 nm at the top portion.
Thereafter, a RIG single crystal film was grown by the LPE method using this SGGG substrate in the same manner as in Example 1. However, since the lattice constant is less than 1.24950 nm, a RIG single crystal of a desired composition is used in this substrate. The film could not be grown. As compared with Example 5, the number of effective substrates is reduced.

［比較例３］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．６９４：０．３３３：４．０２４：０．３０８：０．６４１、および、Ｃａ／Ｍｇ＝０．３３３／０．３０８＝１．０８となるように秤量したこと以外は実施例１と同様にしてＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９５８ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９９２ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００３４ｎｍであった。結晶ボトム部と結晶トップ部における格子定数の差が大きく、ボトム部において１．２４９８５ｎｍの範囲を超えてしまった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させたが、格子定数が１．２４９８５ｎｍを超えた基板なので所望の組成のＲＩＧ単結晶膜を成長させることができなかった。 Comparative Example 3
A raw material of SGGG single crystal is prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.694: 0.333: 4.024: 0.308: 0.641, and Ca / Mg = 0.333 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that measurement was performed so that .308 = 1.08.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top is 1.24958 nm, and the SGGG single crystal obtained from the crystal bottom The lattice constant of the substrate was 1.24992 nm, and the difference in lattice constant between the crystal bottom and the crystal top was 0.00034 nm. The difference in lattice constant between the crystal bottom portion and the crystal top portion is large, and the bottom portion exceeds the range of 1.24985 nm.
After that, a RIG single crystal film was grown by LPE method using this SGGG substrate in the same manner as in Example 1. However, since the lattice constant exceeds 1.24985 nm, a RIG single crystal film of a desired composition is grown. I could not.

［比較例４］
ＳＧＧＧ単結晶の原料を、原子比Ｇｄ：Ｃａ：Ｇａ：Ｍｇ：Ｚｒ＝２．７１０：０．３６６：４．０２４：０．２６７：０．６３３、および、Ｃａ／Ｍｇ＝０．３６６／０．２６７＝１．３７となるように秤量したこと以外は実施例１と同様にしてＳＧＧＧ単結晶を育成した。
次に、実施例１と同様にしてＳＧＧＧ単結晶基板の格子定数を測定すると、結晶トップ部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９５６ｎｍ、結晶ボトム部から得られたＳＧＧＧ単結晶基板の格子定数は１．２４９８７ｎｍで、結晶ボトム部と結晶トップ部における格子定数の差は０．０００３１ｎｍであった。結晶ボトム部と結晶トップ部における格子定数の差が大きく、ボトム部において１．２４９８５ｎｍを超えてしまった。
その後、実施例１と同様に、このＳＧＧＧ基板を用いてＬＰＥ法によりＲＩＧ単結晶膜を成長させたが、格子定数が１．２４９８５ｎｍを超えた基板なので所望の組成のＲＩＧ単結晶膜を成長させることができなかった。 Comparative Example 4
A raw material of SGGG single crystal is prepared by atomic ratio Gd: Ca: Ga: Mg: Zr = 2.710: 0.366: 4.024: 0.267: 0.633, and Ca / Mg = 0.366 / 0. An SGGG single crystal was grown in the same manner as in Example 1 except that measurement was performed so that .267 = 1.37.
Next, when the lattice constant of the SGGG single crystal substrate is measured in the same manner as in Example 1, the lattice constant of the SGGG single crystal substrate obtained from the crystal top is 1.24956 nm, and the SGGG single crystal obtained from the crystal bottom The lattice constant of the substrate was 1.24987 nm, and the difference in lattice constant between the crystal bottom portion and the crystal top portion was 0.00031 nm. The difference in lattice constant between the bottom of the crystal and the top of the crystal is large, and exceeds 1.24985 nm in the bottom.
After that, a RIG single crystal film was grown by LPE method using this SGGG substrate in the same manner as in Example 1. However, since the lattice constant exceeds 1.24985 nm, a RIG single crystal film of a desired composition is grown. I could not.

Figure 0006500807
Figure 0006500807

Figure 0006500807
Figure 0006500807

本発明により得られるＳＧＧＧ単結晶は、結晶トップ部と結晶ボトム部間における格子定数の分布が均一化されていることから、結晶トップ部から得られたＳＧＧＧ基板と結晶ボトム部から得られたＳＧＧＧ基板における格子定数の均一性に優れている。
そして、結晶トップ部から得られたＳＧＧＧ基板と結晶ボトム部から得られたＳＧＧＧ基板の格子定数差が小さいため、結晶トップ部から結晶ボトム部の全域から得られた基板をＬＰＥ法によるＲＩＧ単結晶膜の育成に供することができ、光アイソレータ用ファラデー回転子に用いられるＲＩＧ単結晶膜を低コストで提供できる。 In the SGGG single crystal obtained according to the present invention, the distribution of lattice constant between the crystal top portion and the crystal bottom portion is made uniform, so the SGGG substrate obtained from the crystal top portion and the SGGG obtained from the crystal bottom portion The uniformity of the lattice constant in the substrate is excellent.
Then, since the difference in lattice constant between the SGGG substrate obtained from the crystal top portion and the SGGG substrate obtained from the crystal bottom portion is small, a substrate obtained from the entire crystal top portion to the entire crystal bottom portion is RIG single crystal by LPE method It can be used for film growth, and can provide an RIG single crystal film used for a Faraday rotator for an optical isolator at low cost.

１ 育成炉
２ チャンバー
３ 断熱材
４ 引き上げ軸
５ ホットゾーン
６ 種結晶
７ ＳＧＧＧ単結晶
８ 坩堝
９ 原料融液
１０ 高周波コイル
１１ 結晶トップ部
１２ 結晶ボトム部

Reference Signs List 1 growth furnace 2 chamber 3 heat insulator 4 pulling shaft 5 hot zone 6 seed crystal 7 SGGG single crystal 8 坩 堝 9 raw material melt solution 10 high frequency coil 11 crystal top portion 12 crystal bottom portion

Claims (4)

Ｇｄ、Ｃａ、Ｇａ、Ｍｇ、Ｚｒと酸素からなる原料融液表面に種結晶を接触させて回転させながら引き上げるチョクラルスキー（ＣＺ：Ｃｚｏｃｈｒａｌｓｋｉ）法によりＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶を育成する方法において、
原料は、育成開始時の原料融液が下記組成式（１）で示される組成となる量を用いて、長尺の直胴部を有する単結晶を育成することを特徴とするＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法。
（ＧｄａＣａｂＧａｃＭｇｄＺｒｅ）Ｏ１２ （１）
［但し、組成式（１）中において、ａ＋ｂ＋ｃ＋ｄ＋ｅ＝８、ｂ＋ｄ＝ｅ、１．２５≦ｂ／ｄ≦１．３５、４．０１４≦ｃ≦４．０３４、０．６２９≦ｅ≦０．６３６である。］ The seed crystal is brought into contact with the surface of the raw material melt consisting of Gd, Ca, Ga, Mg, and Zr, and the seed crystal is brought up while rotating while being pulled by the Czochralski method (CZ: Czochralski) CaMgZr-substituted gadolinium gallium garnet (SGGG) single In the method of growing crystals,
The CaMgZr-substituted gadolinium characterized in that a raw material is used to grow a single crystal having a long straight body portion using an amount such that the raw material melt at the start of growth has a composition represented by the following composition formula (1) -A method of growing a gallium garnet (SGGG) single crystal.
(Gd a Ca b Ga c Mg d Zr e ) O 12 (1)
[Wherein, in the composition formula (1), a + b + c + d + e = 8, b + d = e, 1.25 ≦ b / d ≦ 1.35, 4.014 ≦ c ≦ 4.034, 0.629 ≦ e ≦ 0.636 It is. ] 得られる単結晶は、１００ｍｍ以上の長尺の直胴部を有することを特徴とする請求項１に記載のＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法。   The method for growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal according to claim 1, wherein the obtained single crystal has a long straight body portion of 100 mm or more. 原料融液は、固化率がボトム部で３５％以上であることを特徴とする請求項１又は２に記載のＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法。   The method for growing a CaMgZr-substituted gadolinium gallium garnet (SGGG) single crystal according to claim 1 or 2, wherein the raw material melt has a solidification rate of 35% or more in the bottom portion. 得られる単結晶は、結晶ボトム部と結晶トップ部における格子定数の差が０．０００２ｎｍ以下であることを特徴とする請求項１〜３のいずれかに記載のＣａＭｇＺｒ置換型ガドリニウム・ガリウム・ガーネット（ＳＧＧＧ）単結晶の育成方法。

The CaMgZr-substituted gadolinium gallium garnet according to any one of claims 1 to 3, wherein the single crystal obtained has a difference in lattice constant between the crystal bottom portion and the crystal top portion of 0.0002 nm or less. SGGG) A method of growing a single crystal.

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