JP2004323299A

JP2004323299A - Method for manufacturing rare earth-iron garnet-film by liquid phase epitaxial method

Info

Publication number: JP2004323299A
Application number: JP2003120329A
Authority: JP
Inventors: Yosuke Asahara; 陽介浅原; Shuji Osumi; 修司大住; Nobuo Nakamura; 宣夫中村
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 2003-04-24
Filing date: 2003-04-24
Publication date: 2004-11-18

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare earth-iron garnet film by a liquid phase epitaxial method, by which the formation of pits can be suppressed. <P>SOLUTION: The method for manufacturing the rare earth-iron garnet film by the liquid phase epitaxial method comprises bringing a garnet substrate into contact with a lead oxide-based flux melt in a crucible, in which the components of a rare earth-iron garnet are melted, and then growing the crystal of the rare earth-iron garnet film on the substrate. In the method, after obtaining the lead oxide-based flux melt containing the melted components of the rare earth-iron garnet, the time elapsing before the crystal growth is started from the time when cooling-down from the raw material melting temperature is started is set to be within 2.5 h. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、磁気光学デバイスに用いる希土類−鉄ガーネット膜に係り、特に、光通信に用いられる光アイソレータ用の希土類−鉄ガーネット膜の製造方法に関するものである。
【０００２】
【従来の技術】
【０００３】
【特許文献１】
特開平１０−１６７８９５号公報（請求項３、段落番号００１２〜００１３）
【非特許文献１】
日本応用磁気学会第３８回研究会資料（１９８５年）ｐ．５１〜５５
【０００４】
希土類−鉄ガーネット膜（以下、ＲＩＧ膜と記す）のファラデー効果を利用した磁気光学デバイスが精力的に開発されている。その中でも特に光通信における光源への戻り光を遮断する光アイソレータ、あるいは、発電所から消費者までの電力輸送経路である変電所、送電線、配電線に流れる電流により生じる磁界の大きさを測定して異常を発見する光磁界センサなどは既に実用化段階に入り、磁気光学デバイスに用いられるＲＩＧ膜もより安価なものが求められてきている。
【０００５】
このＲＩＧ膜は、通常、液相エピタキシャル法（以下、ＬＰＥ法と示す）によって結晶育成されている。すなわち、ＬＰＥ法によるＲＩＧ膜の結晶育成は、例えば、フラックス成分である酸化鉛、酸化ビスマス、酸化ホウ素と、希土類−鉄ガーネット成分である希土類酸化物、酸化鉄、場合によって非磁性元素の酸化物などを白金ルツボ内に投入し、約９５０℃で融解させた後、ルツボ内の融液温度を希土類−鉄ガーネットの飽和温度以下である結晶育成開始温度（約８５０℃）にまで降温させ、次いで、この融液に、Ｃａ、Ｍｇ、Ｚｒで置換しその格子定数を大きくしたガドリニウム・ガリウム・ガーネット基板（以下、高格子定数ＧＧＧ基板と記す）を接触させ、この高格子定数ＧＧＧ基板上にＲＩＧ膜をエピタキシャル成長させて行われる。
【０００６】
そして、育成されたＲＩＧ膜は、この後、各磁気光学デバイスに合わせて所望の膜厚に研磨加工されて適用される。尚、酸化ビスマスはフラックス成分として説明したが、ビスマスは上記ＲＩＧ膜を構成する元素でもあり、希土類−鉄ガーネット成分でもある。
【０００７】
ところで、このように結晶育成されたＲＩＧ膜の表面には、ピットと呼ばれる三角錐状の結晶欠陥が発生する。このピットも小さいものは上記研磨加工で取り除くことが可能であるが、大きいものは研磨加工後もＲＩＧ膜に黒い点状のシミ（以下、ピット残りと呼ぶ）のように残る。
【０００８】
そして、ピット残りを有するＲＩＧ膜を、例えば光アイソレータに用いた場合には、挿入損失の増大やアイソレーションの低下をもたらし、また、光磁界センサに用いた場合には、センサ出力と測定磁界の直線性に悪影響を及ぼす。
【０００９】
そこで、特許文献１では、ピットの発生原因が融液中に溶け出す白金ルツボの白金であるとし、かつ、９５０℃では白金ルツボから融液中に白金は溶出しないとし、ＲＩＧ膜の育成終了後に速やかに融液の温度を上昇させ、融液を飽和温度以下に保持する時間を短縮することにより、融液中への白金の溶け出しを抑制して上記ピットの発生を防止した方法を提案している。
【００１０】
この方法によってピット密度は数個／ｃｍ^２まで低減することが可能になったが、数個／ｃｍ^２のピット密度では、直径３インチのガーネット基板に育成されるＲＩＧ膜には４０個以上のピットが発生することになる。
【００１１】
【発明が解決しようとする課題】
本発明はこの様な問題点に着目してなされたもので、その課題とするところは、例えば直径３インチのガーネット基板に育成されるＲＩＧ膜全体で、ピット数が数個にまでピットの発生を抑制できる液相エピタキシャル法による希土類−鉄ガーネット膜の製造方法を提供することにある。
【００１２】
【課題を解決するための手段】
ところで、ピットの発生原因の一つに、非特許文献１にも記載されているようにＬＰＥ結晶育成に適用される白金ルツボから融液中に溶け出した白金があり、この白金の微粒子が結晶核となり、ピットが発生すると考えられていた。
【００１３】
しかし、白金の溶出とピットの発生について本発明者らが行った研究結果によると、溶出した白金の微粒子が核となり発生するピットも確かにあるが、融液を飽和温度以下に冷却した際に融液中に析出する微小なＲＩＧがピットの主たる原因であることが判明した。
【００１４】
すなわち、ＬＰＥ法によるＲＩＧ膜の育成では、ＲＩＧ成分を溶解した酸化鉛系フラックス融液を飽和温度以下の過冷却状態とし、このような融液にガーネット基板を接触させることにより、ガーネット基板上にＲＩＧ膜を析出、成長させるが、融液中にＲＩＧの核が析出し、これがガーネット基板ないしガーネット基板上に成長させたＲＩＧ膜上に付着すると面方位の異なるＲＩＧが出現したことになり、ピットのような結晶欠陥が発生することになる。
【００１５】
そこで、融液中にＲＩＧの核が発生する前にＲＩＧの結晶成長を開始させれば、融液中に発生したＲＩＧの核を原因とするピットの発生が抑制されるとの予測の下、鋭意研究を継続した結果、ＲＩＧ成分が溶解した酸化鉛系フラックス融液を得た後、その原料融解温度から降温を開始したときより２．５時間以内にＲＩＧの結晶成長を開始させることにより、融液中に発生したＲＩＧの核を原因とするピットの発生が抑制され、ピットの非常に少ないＲＩＧ膜が得られることを発見するに至った。本発明はこの様な技術的発見に基づき完成されている。
【００１６】
すなわち、請求項１に係る発明は、
希土類−鉄ガーネット成分を酸化鉛系フラックスと共にルツボ内に投入し、投入したこれ等原料を融解させて希土類−鉄ガーネット成分が溶解した酸化鉛系フラックス融液を得、次いで、ルツボ内の融液温度を原料融解温度から希土類−鉄ガーネットの飽和温度以下である結晶育成開始温度まで降温させた後、この融液にガーネット基板を接触させて基板上に希土類−鉄ガーネット膜を結晶育成させる液相エピタキシャル法による希土類−鉄ガーネット膜の製造方法を前提とし、上記原料を融解させて希土類−鉄ガーネット成分が溶解した酸化鉛系フラックス融液を得た後、その原料融解温度から降温を開始したときより結晶育成を開始させるまでの時間を２．５時間以内としたことを特徴とするものである。
【００１７】
【発明の実施の形態】
以下、本発明の実施の形態について詳細に説明する。
【００１８】
ＬＰＥ法によるＲＩＧ膜の結晶育成では、上述したように融液を過冷却状態とするが、過冷却状態で融液を放置すれば、飽和溶解度より過剰なＲＩＧが自然に析出し始める。
【００１９】
そこで、原料融解温度からの降温を開始してから、結晶育成を開始するまでの降温時間を変化させて、結晶育成後のＲＩＧ膜におけるピットの発生数の関係を詳細に調べた。この結果を図１に示すが、図１より降温時間と結晶育成後のピット数が関連していることが確認される。
【００２０】
すなわち、降温時間が２時間まではほとんどピット数の増加は見られないが、２時間より降温時間が長くなると徐々にピット数の増加が見られ、２．５時間を超えると急激にピットが増加していることが確認される。
【００２１】
従って、降温時間を２．５時間以内にすれば、ピットの非常に少ないＲＩＧ膜が得られる。望ましくは２時間以内が好ましい。
【００２２】
また、融液量によって左右されるが、降温時間をあまり短くすると所望の育成開始温度に制御することが難しくなるため、１時間以上が望ましい。
【００２３】
尚、原料融解温度は、結晶育成開始温度より約１００℃ほど高温の９００〜９６０℃が望ましい。高すぎると白金ルツボからの白金の溶出が促進されるため白金起因のピットが発生し、低すぎると原料の融解が不十分となり好ましくない。
【００２４】
【実施例】
以下、本発明の実施例を具体的に説明する。
【００２５】
［実施例１］
白金ルツボ中にＰｂＯ、Ｂｉ_２Ｏ_３、Ｂ_２Ｏ_３をフラックスとし、希土類−鉄ガーネット（ＲＩＧ）成分としてＧｄ_２Ｏ_３、Ｆｅ_２Ｏ_３、Ａｌ_２Ｏ_３、Ｇａ_２Ｏ_３を溶かし込んだ融液を調製した。
【００２６】
この融液を電気炉内で９５０℃（原料融解温度）に加熱し、十分に原料を融解した後、結晶育成開始温度である８１０℃まで２時間１５分で降温させ、次いで、融液表面にＣａ、Ｍｇ、Ｚｒで置換した直径３インチのガドリニウム・ガリウム・ガーネット基板（高格子定数ＧＧＧ基板）を接触させ、かつ、この基板を１００ｒｐｍで回転させて、基板の片面に厚さ５５０μｍでかつ組成が（ＧｄＢｉ）_３（ＦｅＡｌＧａ）_５Ｏ_１２のＲＩＧ膜を５枚育成した。
【００２７】
そして、結晶育成させたＲＩＧ膜の表面を光学顕微鏡で観察し、直径３インチのガーネット基板に育成されたＲＩＧ膜全体のピット個数を調べたところ、表１に示すようにピット個数を１０個以下にすることができた。
【００２８】
［実施例２］
ＲＩＧ成分としてＴｂ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３を用い、かつ、結晶育成開始温度を８３０℃としたこと以外は実施例１と同様にして、高格子定数ＧＧＧ基板の片面に厚さ５００μｍでかつ組成が（ＹｂＴｂＢｉ）_３Ｆｅ_５Ｏ_１２のＲＩＧ膜を５枚育成した。また、原料融解温度から結晶育成開始温度までの降温時間は２時間１５分とした。
【００２９】
そして、結晶育成させたＲＩＧ膜の表面を光学顕微鏡で観察し、直径３インチのガーネット基板に育成されたＲＩＧ膜全体のピット個数を調べたところ、表１に示すようにピット個数を１０個以下にすることができた。
【００３０】
［実施例３］
ＲＩＧ成分としてＧｄ_２Ｏ_３、Ａｌ_２Ｏ_３、Ｆｅ_２Ｏ_３を用い、かつ、結晶育成開始温度を８６０℃とし、更に、原料融解温度から結晶育成開始温度までの降温時間を２時間３０分とした以外は実施例１と同様にして、高格子定数ＧＧＧ基板の片面に厚さ５５０μｍでかつ組成が（ＧｄＢｉ）_３（ＦｅＡｌ）_５Ｏ_１２のＲＩＧ膜を５枚育成した。
【００３１】
そして、結晶育成させたＲＩＧ膜の表面を光学顕微鏡で観察し、直径３インチのガーネット基板に育成されたＲＩＧ膜全体のピット個数を調べたところ、表１に示すようにピット個数を１０個以下にすることができた。
【００３２】
［比較例１］
融解温度から育成開始温度までの降温時間を３時間とした以外は実施例１と同様にして、厚さ５５０μｍでかつ組成が（ＧｄＢｉ）_３（ＦｅＡｌＧａ）_５Ｏ_１２のＲＩＧ膜を５枚育成した。
【００３３】
そして、結晶育成させたＲＩＧ膜の表面を光学顕微鏡で観察し、直径３インチのガーネット基板に育成されたＲＩＧ膜全体のピット個数を調べたところ、表１に示すようにピット個数が１０個以上になっていることが確認される。
【００３４】
［比較例２］
融解温度から育成開始温度までの降温時間を３時間とした以外は実施例２と同様にして、厚さ５００μｍでかつ組成が（ＹｂＴｂＢｉ）_３Ｆｅ_５Ｏ_１２のＲＩＧ膜を５枚育成した。
【００３５】
そして、結晶育成させたＲＩＧ膜の表面を光学顕微鏡で観察し、直径３インチのガーネット基板に育成されたＲＩＧ膜全体のピット個数を調べたところ、表１に示すようにピット個数が１０個以上になっていることが確認される。
【００３６】
［比較例３］
融解温度から育成開始温度までの降温時間を３時間とした以外は実施例３と同様にして、厚さ５５０μｍでかつ組成が（ＧｄＢｉ）_３（ＦｅＡｌ）_５Ｏ_１２のＲＩＧ膜を５枚育成した。
【００３７】
そして、結晶育成させたＲＩＧ膜の表面を光学顕微鏡で観察し、直径３インチのガーネット基板に育成されたＲＩＧ膜全体のピット個数を調べたところ、表１に示すようにピット個数が１０個以上になっていることが確認される。
【００３８】
【表１】

【００３９】
【発明の効果】
請求項１記載の発明に係る液相エピタキシャル法による希土類−鉄ガーネット膜の製造方法によれば、原料を融解させて希土類−鉄ガーネット成分が溶解した酸化鉛系フラックス融液を得た後、その原料融解温度から降温を開始したときより結晶育成を開始させるまでの時間を２．５時間以内としているため、ピットと呼ばれる三角錐状の結晶欠陥による特性不良が極めて少ない、光アイソレータや光磁界センサ等に適用される希土類−鉄ガーネット膜を容易に製造することができる効果を有している。
【図面の簡単な説明】
【図１】降温時間とピット個数との関係を示すグラフ図。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rare earth-iron garnet film used for a magneto-optical device, and more particularly to a method for manufacturing a rare earth-iron garnet film for an optical isolator used for optical communication.
[0002]
[Prior art]
[0003]
[Patent Document 1]
JP-A-10-167895 (Claim 3, paragraphs 0012 to 0013)
[Non-patent document 1]
Materials of the 38th meeting of the Japan Society of Applied Magnetics (1985), p. 51-55
[0004]
Magneto-optical devices utilizing the Faraday effect of a rare earth-iron garnet film (hereinafter referred to as an RIG film) have been vigorously developed. In particular, it measures the magnitude of the magnetic field generated by the current flowing through the optical isolator that blocks the return light to the light source in optical communication, or the substation, transmission line, and distribution line that is the power transport route from the power plant to the consumer. Optical magnetic field sensors that detect abnormalities have entered the stage of practical use, and RIG films used in magneto-optical devices are also required to be cheaper.
[0005]
This RIG film is usually grown by a liquid phase epitaxial method (hereinafter, referred to as an LPE method). That is, the crystal growth of the RIG film by the LPE method includes, for example, lead oxide, bismuth oxide, and boron oxide as flux components, rare earth oxide and iron oxide as rare earth-iron garnet components, and oxides of nonmagnetic elements in some cases. After melting into a platinum crucible and melting at about 950 ° C., the temperature of the melt in the crucible is lowered to a crystal growth starting temperature (about 850 ° C.) which is equal to or lower than the rare earth-iron garnet saturation temperature, A gadolinium-gallium-garnet substrate (hereinafter, referred to as a high lattice constant GGG substrate) which has been replaced with Ca, Mg, and Zr and has a large lattice constant is brought into contact with the melt, and RIG is placed on the high lattice constant GGG substrate. This is performed by epitaxially growing a film.
[0006]
Then, the grown RIG film is thereafter polished to a desired film thickness in accordance with each magneto-optical device and applied. Although bismuth oxide has been described as a flux component, bismuth is also an element constituting the RIG film, and is also a rare earth-iron garnet component.
[0007]
By the way, triangular pyramid-shaped crystal defects called pits occur on the surface of the RIG film grown as described above. Small pits can be removed by the above-mentioned polishing, but large pits remain on the RIG film as black spots (hereinafter referred to as pit residues) even after the polishing.
[0008]
When the RIG film having the pit residue is used for an optical isolator, for example, the insertion loss increases and the isolation decreases, and when the RIG film is used for an optical magnetic field sensor, the sensor output and the measured magnetic field are reduced. Affects linearity.
[0009]
Therefore, in Patent Document 1, it is assumed that the pits are caused by platinum of a platinum crucible that dissolves into the melt, and that platinum is not eluted from the platinum crucible at 950 ° C. into the melt. By raising the temperature of the melt promptly and shortening the time for keeping the melt below the saturation temperature, a method was proposed in which the pits were prevented from being generated by suppressing the dissolution of platinum into the melt. ing.
[0010]
Although pit density became can be reduced to several / cm ² by this method, the pit density of several / cm ^2, the RIG film to be grown on a garnet substrate of 3 inches in diameter more than 40 A pit will occur.
[0011]
[Problems to be solved by the invention]
The present invention has been made in view of such a problem, and an object of the present invention is to generate pits up to several pits in an entire RIG film grown on a garnet substrate having a diameter of, for example, 3 inches. It is an object of the present invention to provide a method for producing a rare earth-iron garnet film by a liquid phase epitaxial method capable of suppressing the occurrence of garnet.
[0012]
[Means for Solving the Problems]
Incidentally, as described in Non-Patent Document 1, one of the causes of the pits is platinum dissolved in a melt from a platinum crucible used for growing LPE crystals, and the fine particles of the platinum form crystals. It was thought to be a nucleus and pits.
[0013]
However, according to the results of research conducted by the present inventors on the elution of platinum and the generation of pits, there are certainly pits generated by eluted platinum fine particles as nuclei, but when the melt is cooled below the saturation temperature, It was found that minute RIG precipitated in the melt was the main cause of pits.
[0014]
That is, in growing the RIG film by the LPE method, the lead oxide-based flux melt in which the RIG component is dissolved is placed in a supercooled state at a saturation temperature or lower, and the garnet substrate is brought into contact with such a melt, thereby forming a garnet substrate. The RIG film is deposited and grown. When RIG nuclei precipitate in the melt and adhere to the garnet substrate or the RIG film grown on the garnet substrate, RIGs having different plane orientations appear, and pits are formed. Such a crystal defect as described above occurs.
[0015]
Therefore, if the crystal growth of RIG is started before the nucleus of RIG is generated in the melt, it is predicted that the generation of pits caused by the nucleus of RIG generated in the melt is suppressed. As a result of continuing intensive research, after obtaining a lead oxide-based flux melt in which the RIG component is dissolved, by starting crystal growth of the RIG within 2.5 hours from when the temperature is lowered from the raw material melting temperature, It has been found that the generation of pits caused by RIG nuclei generated in the melt is suppressed, and an RIG film having very few pits can be obtained. The present invention has been completed based on such technical findings.
[0016]
That is, the invention according to claim 1 is
The rare earth-iron garnet component is introduced into the crucible together with the lead oxide-based flux, and the raw materials thus added are melted to obtain a lead oxide-based flux melt in which the rare earth-iron garnet component is dissolved. After the temperature is lowered from the raw material melting temperature to the crystal growth start temperature which is equal to or lower than the saturation temperature of the rare earth-iron garnet, a liquid phase for bringing a garnet substrate into contact with the melt to grow a rare earth-iron garnet film on the substrate. Assuming a method of manufacturing a rare earth-iron garnet film by an epitaxial method, after the above-mentioned raw material is melted to obtain a lead oxide-based flux melt in which a rare earth-iron garnet component is dissolved, when the temperature is lowered from the raw material melting temperature. The time required to start crystal growth is set to 2.5 hours or less.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0018]
In the crystal growth of the RIG film by the LPE method, the melt is placed in a supercooled state as described above, but if the melt is left in the supercooled state, RIG in excess of the saturation solubility starts to spontaneously precipitate.
[0019]
Therefore, the relationship between the number of pits generated in the RIG film after the crystal growth was examined in detail by changing the temperature lowering time from the start of the temperature lowering from the raw material melting temperature to the start of the crystal growth. The results are shown in FIG. 1, and it is confirmed from FIG. 1 that the cooling time is related to the number of pits after crystal growth.
[0020]
That is, the number of pits is hardly increased until the cooling time is 2 hours, but the number of pits is gradually increased when the cooling time is longer than 2 hours, and the number of pits is rapidly increased after 2.5 hours. Is confirmed.
[0021]
Therefore, if the cooling time is set within 2.5 hours, an RIG film with very few pits can be obtained. Desirably, it is within 2 hours.
[0022]
Further, although it depends on the amount of the melt, if the cooling time is too short, it becomes difficult to control the growth start temperature to a desired growth start temperature.
[0023]
In addition, the raw material melting temperature is desirably 900 to 960 ° C., which is about 100 ° C. higher than the crystal growth start temperature. If the temperature is too high, the elution of platinum from the platinum crucible is promoted, so that pits due to platinum occur.
[0024]
【Example】
Hereinafter, examples of the present invention will be specifically described.
[0025]
[Example 1]
_PbO, a _{_{_{Bi 2 O 3, B 2 O}}} 3 and flux in a platinum crucible, the rare earth - _Gd 2 _O 3 as an iron garnet (RIG) _{_{_{_{component, Fe 2 O 3, Al 2}}}} O 3, elaborate dissolved _Ga 2 _{O 3} A melt was prepared.
[0026]
This melt is heated to 950 ° C. (raw material melting temperature) in an electric furnace, and after sufficiently melting the raw material, the temperature is lowered to 810 ° C., which is the crystal growth start temperature, for 2 hours and 15 minutes. A gadolinium gallium garnet substrate (high lattice constant GGG substrate) having a diameter of 3 inches replaced with Ca, Mg, and Zr is brought into contact with the substrate, and the substrate is rotated at 100 rpm to form a 550 μm-thick composition on one surface of the substrate. Grew _five RIG films of (GdBi) ₃ (FeAlGa) ₅ O ₁₂ .
[0027]
Then, the surface of the crystal-grown RIG film was observed with an optical microscope, and the number of pits in the entire RIG film grown on a garnet substrate having a diameter of 3 inches was examined. As shown in Table 1, the number of pits was 10 or less. I was able to.
[0028]
[Example 2]
Except that Tb ₂ O ₃ , Yb ₂ O ₃ , and Fe ₂ O ₃ were used as the RIG components and the crystal growth start temperature was set to 830 ° C., a high lattice constant GGG substrate was formed on one surface in the same manner as in Example 1. _Five RIG films having a thickness of 500 μm and a composition of (YbTbBi) ₃ Fe ₅ O ₁₂ were grown. The temperature drop time from the raw material melting temperature to the crystal growth start temperature was 2 hours and 15 minutes.
[0029]
Then, the surface of the crystal-grown RIG film was observed with an optical microscope, and the number of pits in the entire RIG film grown on a garnet substrate having a diameter of 3 inches was examined. As shown in Table 1, the number of pits was 10 or less. I was able to.
[0030]
[Example 3]
Gd ₂ O ₃ , Al ₂ O ₃ , and Fe ₂ O ₃ are used as RIG components, and the crystal growth start temperature is 860 ° C. Further, the temperature drop time from the raw material melting temperature to the crystal growth start temperature is 2 hours 30 minutes. In the same manner as in Example 1, five RIG films each having a thickness of 550 μm and a composition of (GdBi) ₃ (FeAl) ₅ O ₁₂ were grown on one surface of the GGG substrate except that the above was adopted.
[0031]
Then, the surface of the crystal-grown RIG film was observed with an optical microscope, and the number of pits in the entire RIG film grown on a garnet substrate having a diameter of 3 inches was examined. As shown in Table 1, the number of pits was 10 or less. I was able to.
[0032]
[Comparative Example 1]
Five RIG films having a thickness of 550 μm and a composition of (GdBi) ₃ (FeAlGa) ₅ O ₁₂ were grown in the same manner as in Example 1 except that the temperature drop time from the melting temperature to the growth start temperature was set to 3 hours. .
[0033]
The surface of the grown RIG film was observed with an optical microscope, and the number of pits in the entire RIG film grown on a garnet substrate having a diameter of 3 inches was examined. As shown in Table 1, the number of pits was 10 or more. Is confirmed.
[0034]
[Comparative Example 2]
_Five RIG films having a thickness of 500 μm and a composition of (YbTbBi) ₃ Fe ₅ O ₁₂ were grown in the same manner as in Example 2 except that the temperature drop time from the melting temperature to the growth start temperature was 3 hours.
[0035]
The surface of the grown RIG film was observed with an optical microscope, and the number of pits in the entire RIG film grown on a garnet substrate having a diameter of 3 inches was examined. As shown in Table 1, the number of pits was 10 or more. Is confirmed.
[0036]
[Comparative Example 3]
Five RIG films having a thickness of 550 μm and a composition of (GdBi) ₃ (FeAl) ₅ O ₁₂ were grown in the same manner as in Example 3, except that the temperature drop time from the melting temperature to the growth start temperature was 3 hours. .
[0037]
The surface of the grown RIG film was observed with an optical microscope, and the number of pits in the entire RIG film grown on a garnet substrate having a diameter of 3 inches was examined. As shown in Table 1, the number of pits was 10 or more. Is confirmed.
[0038]
[Table 1]

[0039]
【The invention's effect】
According to the method for producing a rare earth-iron garnet film by a liquid phase epitaxial method according to the invention of claim 1, after melting a raw material to obtain a lead oxide-based flux melt in which a rare earth-iron garnet component is dissolved, Since the time from when the temperature is lowered from the raw material melting temperature to when the crystal growth is started is set to 2.5 hours or less, there is very little characteristic failure due to triangular pyramid-shaped crystal defects called pits. This has the effect that a rare earth-iron garnet film applied to the above-described method can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between a cooling time and the number of pits.

Claims

The rare earth-iron garnet component is introduced into the crucible together with the lead oxide-based flux, and the raw materials thus added are melted to obtain a lead oxide-based flux melt in which the rare earth-iron garnet component is dissolved. After the temperature is lowered from the raw material melting temperature to the crystal growth start temperature which is equal to or lower than the saturation temperature of the rare earth-iron garnet, a liquid phase for bringing a garnet substrate into contact with the melt to grow a rare earth-iron garnet film on the substrate. In a method for producing a rare earth-iron garnet film by an epitaxial method,
After obtaining the lead oxide-based flux melt in which the raw material is melted and the rare earth-iron garnet component is dissolved, the time from when the temperature is lowered from the raw material melting temperature to when the crystal growth is started is 2.5 hours or less. A method for producing a rare earth-iron garnet film by a liquid phase epitaxy method.