JP2007210879A

JP2007210879A - Magnetic garnet single crystal, its production method, and optical element using the same

Info

Publication number: JP2007210879A
Application number: JP2006314086A
Authority: JP
Inventors: Atsushi Oido; 敦大井戸
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2006-01-10
Filing date: 2006-11-21
Publication date: 2007-08-23
Anticipated expiration: 2026-11-21
Also published as: JP4802995B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic garnet single crystal reduced in Pb content, its production method and an optical element using the same. <P>SOLUTION: This magnetic garnet single crystal is represented by the chemical formula, Bi<SB>α</SB>Na<SB>β</SB>M1<SB>3-α-β</SB>Fe<SB>5-γ</SB>M2<SB>γ</SB>O<SB>12</SB>(wherein M1 is at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; M2 is at least one element selected from Si, Ge and Ti; 0.5<α≤2.0; 0<β≤0.8; 0.2≤3-α-β<2.5; and 0<γ≤1.6). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、磁性ガーネット単結晶及びその製造方法並びにそれを用いた光学素子に関する。 The present invention relates to a magnetic garnet single crystal, a method for producing the same, and an optical element using the same.

ファラデー回転子は、透過する光の偏光面を回転させる機能を有する光学素子であり、通信用光アイソレータ、光アッテネータ、光サーキュレータ、光磁界センサ等の光デバイスに使用される。ファラデー回転子は、一般に板状のビスマス（Ｂｉ）置換希土類鉄ガーネット単結晶を用いて作製される。Ｂｉ置換希土類鉄ガーネット単結晶は、フラックス法の一種である液相エピタキシャル（ＬＰＥ）法により育成される。フラックス法による単結晶育成は、大気圧中で行われる。 The Faraday rotator is an optical element having a function of rotating a polarization plane of transmitted light, and is used for an optical device such as a communication optical isolator, an optical attenuator, an optical circulator, and an optical magnetic field sensor. A Faraday rotator is generally manufactured using a plate-like bismuth (Bi) -substituted rare earth iron garnet single crystal. Bi-substituted rare earth iron garnet single crystal is grown by a liquid phase epitaxial (LPE) method which is a kind of flux method. Single crystal growth by the flux method is performed at atmospheric pressure.

フラックス法等の溶液法によりＢｉ置換希土類鉄ガーネット単結晶を育成する際には、過飽和状態を保ちながらガーネット単結晶を安定に成長させるために、一般に酸化鉛（ＰｂＯ）、酸化ビスマス（Ｂｉ_２Ｏ_３）及び酸化ホウ素（Ｂ_２Ｏ_３）が溶媒として用いられる。このため磁性ガーネット単結晶の育成時には結晶中に少量の鉛（Ｐｂ）が混入する。従来、通信用光デバイスに使用されるファラデー回転子には、化学式Ｂｉ_{３−ｘ−ｙ}Ｍ１_ｘＰｂ_ｙＦｅ_{５−ｚ−ｗ}Ｍ２_ｚＭ３_ｗＯ_１２においてＰｂの量ｙが０．０３〜０．０６程度である磁性ガーネット単結晶が用いられている。
特開２００１−０４４０２６号公報特開２００１−０４４０２７号公報特公平６−０４６６０４号公報 When a Bi-substituted rare earth iron garnet single crystal is grown by a solution method such as a flux method, lead oxide (PbO) or bismuth oxide (Bi ₂ O) is generally used to stably grow the garnet single crystal while maintaining a supersaturated state. ₃ ) and boron oxide (B ₂ O ₃ ) are used as solvents. For this reason, when growing a magnetic garnet single crystal, a small amount of lead (Pb) is mixed in the crystal. Conventionally, the Faraday rotator to be used for communication optical device, in the chemical formula _{_{_{_{Bi 3-x-y M1 x}}}} Pb y Fe 5-z-w M2 z M3 w O 12 quantity y of Pb is 0.03 to 0 A magnetic garnet single crystal of about .06 is used.
JP 2001-044026 A JP 2001-044027 A Japanese Examined Patent Publication No. 6-046604

ところが近年の環境保護運動の高まりと共に、全ての工業製品で環境負荷物質であるＰｂの含有量を削減する努力がなされている。従って、ＬＰＥ法により育成する磁性ガーネット単結晶においても、少量ではあるが混入するＰｂが環境汚染の要因になり得るとして問題になってきた。そこでファラデー回転子を構成する材料である磁性ガーネット単結晶に含有するＰｂの量を削減又は除去する必要が生じている。 However, with the recent increase in environmental protection movement, efforts are being made to reduce the content of Pb, which is an environmentally hazardous substance, in all industrial products. Therefore, even in a magnetic garnet single crystal grown by the LPE method, a small amount of Pb mixed therein has become a problem because it can cause environmental pollution. Therefore, it is necessary to reduce or remove the amount of Pb contained in the magnetic garnet single crystal that is a material constituting the Faraday rotator.

本発明の目的は、Ｐｂの含有量を削減した磁性ガーネット単結晶及びその製造方法並びにそれを用いた光学素子を提供することにある。 An object of the present invention is to provide a magnetic garnet single crystal with a reduced Pb content, a method for producing the same, and an optical element using the same.

上記目的は、化学式Ｂｉ_αＮａ_βＭ１_{３−α−β}Ｆｅ_5-γＭ２_γＯ_１２（Ｍ１はＹ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕから選択される少なくとも１種類以上の元素、Ｍ２はＳｉ、Ｇｅ、Ｔｉから選択される少なくとも１種類以上の元素であり、０．５＜α≦２．０、０＜β≦０．８、０．２≦３−α−β＜２．５、０＜γ≦１．６）で示されることを特徴とする磁性ガーネット単結晶によって達成される。 The above object has the formula _{_{_{Bi α Na β M1 3-α}}} -β Fe 5-γ M2 γ O 12 (M1 is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one element selected from Tm, Yb, Lu, M2 is at least one element selected from Si, Ge, Ti, 0.5 <α ≦ 2.0, 0 <β ≦ 0.8, 0.2 ≦ 3-α−β <2.5, 0 <γ ≦ 1.6). This is achieved by a magnetic garnet single crystal.

上記本発明の磁性ガーネット単結晶であって、前記γは、０．００７≦γ≦１．６であることを特徴とする。 In the magnetic garnet single crystal of the present invention, γ is 0.007 ≦ γ ≦ 1.6.

また上記目的は、上記本発明の磁性ガーネット単結晶を用いて作製されることを特徴とする光学素子によって達成される。 Further, the above object is achieved by an optical element produced using the magnetic garnet single crystal of the present invention.

さらに上記目的は、Ｎａ、Ｆｅ、Ｍ１及びＭ２（Ｍ１はＹ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕから選択される少なくとも１種類以上の元素、Ｍ２はＳｉ、Ｇｅ、Ｔｉから選択される少なくとも１種類以上の元素）を含む材料から融液を生成し、前記融液を用いて磁性ガーネット単結晶を育成することを特徴とする磁性ガーネット単結晶の製造方法によって達成される。 Further, the object is to provide at least one selected from Na, Fe, M1 and M2 (M1 is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) It is characterized in that a melt is generated from a material containing at least one kind of element, M2 being at least one element selected from Si, Ge, and Ti, and a magnetic garnet single crystal is grown using the melt. This is achieved by a method for producing a magnetic garnet single crystal.

上記本発明の磁性ガーネット単結晶の製造方法であって、前記材料における前記Ｍ２のＦｅに対するモル比は、０．００４以上であることを特徴とする。 In the method for producing a magnetic garnet single crystal of the present invention, a molar ratio of the M2 to Fe in the material is 0.004 or more.

上記本発明の磁性ガーネット単結晶であって、前記β及びγは、０＜β≦０．１、０＜γ≦０．２であることを特徴とする。さらには、前記β及びγは、０＜β≦０．０５、０＜γ≦０．１であることを特徴とする。また、前記Ｍ２は、少なくともＳｉを含む１種類以上の元素であることを特徴とする。
さらに上記目的は、化学式Ｂｉ_αＮａ_βＭ１_{３−α−β}Ｆｅ_5-γ-σＭ２_γＭ３_δＯ_１２（Ｍ１はＹ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕから選択される少なくとも１種類以上の元素、Ｍ２はＳｉ、Ｇｅ、Ｔｉから選択される少なくとも１種類以上の元素、Ｍ３はＰｔであり、０．５＜α≦２．０、０＜β≦０．８、０．２≦３−α−β＜２．５、０＜γ＋δ≦１．６、０≦γ＜１．６、０＜δ＜０．１６）で示されることを特徴とする磁性ガーネット単結晶によって達成される。
また上記目的は、上記本発明の磁性ガーネット単結晶から作製されることを特徴とするファラデー回転子によって達成される。 In the magnetic garnet single crystal of the present invention, β and γ are 0 <β ≦ 0.1 and 0 <γ ≦ 0.2. Furthermore, the β and γ are 0 <β ≦ 0.05 and 0 <γ ≦ 0.1. The M2 is one or more kinds of elements including at least Si.
Further above object, the chemical formula _{_{_{Bi α Na β M1 3-α}}} -β Fe 5-γ-σ M2 γ M3 δ O 12 (M1 is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb, Lu, M2 is at least one element selected from Si, Ge, Ti, M3 is Pt, and 0.5 <α ≦ 2.0, 0 <β ≦ 0.8, 0.2 ≦ 3-α−β <2.5, 0 <γ + δ ≦ 1.6, 0 ≦ γ <1.6, 0 <δ <0.16 It is achieved by a magnetic garnet single crystal characterized by the following.
The above-mentioned object is achieved by a Faraday rotator which is produced from the magnetic garnet single crystal of the present invention.

本発明によれば、磁性ガーネット単結晶に含まれるＰｂ量を削減し、あるいは完全に除去することができる。 According to the present invention, the amount of Pb contained in the magnetic garnet single crystal can be reduced or completely removed.

〔第１の実施の形態〕
本発明の第１の実施の形態による磁性ガーネット単結晶及びその製造方法並びにそれを用いた光学素子について図１及び図２を用いて説明する。本実施の形態では、従来の溶媒に含まれるＰｂをナトリウム（Ｎａ）で代替し、Ｎａ及び鉄（Ｆｅ）を含む溶媒から磁性ガーネット単結晶を育成する。Ｎａと酸素とを含有する物質は他の酸化物に比べて低い温度で溶解するものが多いため、磁性ガーネット単結晶を育成する際の溶媒としても有効である。例えば水酸化ナトリウム（ＮａＯＨ）を含む溶媒から育成された磁性ガーネット単結晶は、欠陥や割れのない優れた品質が得られる。そのため溶媒の材料からＰｂＯを除外し、Ｎａを含む物質とＢｉ_２Ｏ_３及びＢ_２Ｏ_３を溶媒に用いることにより、従来磁性ガーネット単結晶に微量含まれていたＰｂをほぼ完全に除去できる。 [First Embodiment]
A magnetic garnet single crystal according to a first embodiment of the present invention, a manufacturing method thereof, and an optical element using the same will be described with reference to FIGS. In this embodiment, Pb contained in a conventional solvent is replaced with sodium (Na), and a magnetic garnet single crystal is grown from a solvent containing Na and iron (Fe). Since many substances containing Na and oxygen dissolve at a lower temperature than other oxides, they are also effective as solvents for growing magnetic garnet single crystals. For example, a magnetic garnet single crystal grown from a solvent containing sodium hydroxide (NaOH) has excellent quality without defects or cracks. Therefore, by removing PbO from the solvent material and using a substance containing Na and Bi ₂ O ₃ and B ₂ O ₃ as the solvent, it is possible to almost completely remove Pb that has been contained in a trace amount in the conventional magnetic garnet single crystal.

ところが、Ｎａを含む溶媒から育成したガーネット単結晶は、光通信で使用される１３００〜１６００ｎｍの波長帯域での光吸収が極めて大きいということが判明した。大きな光吸収を持つガーネット単結晶を加工してファラデー回転子等の光学素子を作製すると、光学素子の光損失（挿入損失）が高くなってしまうという問題が生じ得る。したがって、Ｐｂがほぼ完全に除去された光学素子の光損失を低減させるために、Ｎａを含む溶媒を用いて育成されるガーネット単結晶の光吸収を減少させる必要がある。 However, it has been found that a garnet single crystal grown from a solvent containing Na has extremely large light absorption in a wavelength band of 1300 to 1600 nm used in optical communication. When an optical element such as a Faraday rotator is manufactured by processing a garnet single crystal having a large light absorption, there may be a problem that the optical loss (insertion loss) of the optical element increases. Therefore, in order to reduce the optical loss of the optical element from which Pb is almost completely removed, it is necessary to reduce the light absorption of the garnet single crystal grown using the solvent containing Na.

ここで、ＮａＯＨ、Ｂｉ_２Ｏ_３及びＢ_２Ｏ_３を含む溶媒からＬＰＥ法により育成した（ＢｉＧｄＹｂ）_３Ｆｅ_５Ｏ_１２単結晶を加工して、ファラデー回転子を作製した。このファラデー回転子の波長１．５５μｍの光に対する光損失は３ｄＢであった。また、Ｐｂを含む溶媒からＬＰＥ法により育成した（ＢｉＧｄＹｂ）_３Ｆｅ_５Ｏ_１２単結晶を加工して、別のファラデー回転子を作製した。このファラデー回転子の波長１．５５μｍの光に対する光損失は０．０５ｄＢ以下であった。したがって、Ｎａを含む溶媒を用いて作製されたファラデー回転子の光損失は、Ｐｂを含む溶媒を用いて作製されたファラデー回転子の光損失と比較して極めて高いことが分かった。蛍光Ｘ線分析で組成を調べたところ、Ｎａを含む溶媒から育成したガーネット単結晶からは１００〜３００ｐｐｍ程度のＮａが検出された。Ｂｉ置換希土類鉄ガーネットを構成するカチオン（陽イオン）は、基本的に３価である。このため、１価が安定な価数であるＮａのカチオンがガーネット単結晶中に入ると、電荷のバランスが崩れてガーネット単結晶が半導体となる。これにより、Ｎａを含むガーネット単結晶では光吸収が発生していると考えられる。 Here, a (BiGdYb) ₃ Fe ₅ O ₁₂ single crystal grown by a LPE method from a solvent containing NaOH, Bi ₂ O ₃ and B ₂ O ₃ was processed to produce a Faraday rotator. The optical loss of this Faraday rotator with respect to light having a wavelength of 1.55 μm was 3 dB. In addition, another Faraday rotator was produced by processing a (BiGdYb) ₃ Fe ₅ O ₁₂ single crystal grown from a solvent containing Pb by the LPE method. The optical loss of this Faraday rotator with respect to light having a wavelength of 1.55 μm was 0.05 dB or less. Therefore, it was found that the optical loss of the Faraday rotator manufactured using the solvent containing Na is extremely higher than the optical loss of the Faraday rotator manufactured using the solvent containing Pb. When the composition was examined by fluorescent X-ray analysis, Na of about 100 to 300 ppm was detected from a garnet single crystal grown from a solvent containing Na. The cation (cation) constituting the Bi-substituted rare earth iron garnet is basically trivalent. For this reason, when a cation of Na, which is a monovalent valence, enters the garnet single crystal, the charge balance is lost and the garnet single crystal becomes a semiconductor. Thereby, it is considered that light absorption occurs in the garnet single crystal containing Na.

本実施の形態では、酸化ケイ素（ＳｉＯ_２）、酸化ゲルマニウム（ＧｅＯ_２）、酸化チタン（ＴｉＯ_２）及び酸化白金（ＰｔＯ_２）のうち少なくとも１種をＮａと共に配合材料に加え、ガーネット単結晶を育成した。育成したガーネット単結晶をファラデー回転子に加工して光損失を評価したところ、光損失が低下する傾向が認められた。Ｓｉ、Ｇｅ、Ｔｉ及びＰｔはガーネット中で４価のカチオンが安定となるため、ガーネット中に含有されるＮａの１価のカチオンを補償することにより、ガーネット単結晶の電荷のバランスがとれるようになったためと考えられる。 In this embodiment, at least one of silicon oxide (SiO ₂ ), germanium oxide (GeO ₂ ), titanium oxide (TiO ₂ ), and platinum oxide (PtO ₂ ) is added to the compounding material together with Na, and a garnet single crystal is added. I grew up. When the grown garnet single crystal was processed into a Faraday rotator and the optical loss was evaluated, a tendency for the optical loss to decrease was observed. Since Si, Ge, Ti, and Pt have a stable tetravalent cation in the garnet, the charge of the garnet single crystal can be balanced by compensating for the monovalent cation of Na contained in the garnet. It is thought that it became.

さらに本実施の形態では、Ｎａを含む配合材料にＧｅＯ_２を種々の配合量で加えて、複数種類のガーネット単結晶を育成した。本実施の形態では、配合材料中におけるＧｅのＦｅに対するモル比（Ｇｅ／Ｆｅモル比）をパラメータとして用い、Ｇｅ／Ｆｅモル比を０〜０．０２の範囲内で種々の値に設定した。育成した複数種類のガーネット単結晶をそれぞれファラデー回転子に加工し、光損失を評価した。その結果、配合材料にＧｅＯ_２をわずかに添加するだけでもファラデー回転子の光損失は大幅に低下し、Ｇｅ／Ｆｅモル比が０．００４の配合材料を用いて作製したファラデー回転子の光損失は、０〜０．０１ｄＢと極めて低くなることが分かった。Ｇｅ／Ｆｅモル比を０．００４より大きくしても、ファラデー回転子の光損失は０〜０．０１ｄＢで変化はなかった。 Further, in this embodiment, by adding GeO ₂ in various amounts to the formulation material containing Na, it was grown several types of garnet single crystal. In the present embodiment, the molar ratio of Ge to Fe (Ge / Fe molar ratio) in the blended material was used as a parameter, and the Ge / Fe molar ratio was set to various values within the range of 0 to 0.02. Multiple types of grown garnet single crystals were processed into Faraday rotators, and the optical loss was evaluated. As a result, the optical loss of the Faraday rotator is significantly reduced by adding a small amount of GeO ₂ to the compounding material, and the optical loss of the Faraday rotator manufactured using the compounding material having a Ge / Fe molar ratio of 0.004. Was found to be extremely low, 0-0.01 dB. Even when the Ge / Fe molar ratio was larger than 0.004, the optical loss of the Faraday rotator was 0 to 0.01 dB, and there was no change.

Ｇｅ／Ｆｅモル比が０．００４である配合材料から育成したガーネット単結晶を蛍光Ｘ線分析及びＩＣＰ（ＩｎｄｕｃｔｉｖｅｌｙＣｏｕｐｌｅｄＰｌａｓｍａ；高周波誘導結合プラズマ）分析により組成分析したところ、化学式（ＢｉＧｄＹｂ）_{２．９９６}Ｎａ_{０．００４}Ｆｅ_{４．９９３}Ｇｅ_{０．００７}Ｏ_１２が得られた。したがって、Ｇｅのようにガーネット中で４価が安定な元素がガーネット単結晶中に入ることによってファラデー回転子の光損失が低下し、特にガーネット単結晶中のＧｅ量を化学式で０．００７にするとファラデー回転子の光損失を最低にすることができることが分かった。そしてガーネット単結晶中のＧｅ量をさらに増加させてもファラデー回転子の光損失は最低値のままである。 A garnet single crystal grown from a compound material having a Ge / Fe molar ratio of 0.004 was subjected to compositional analysis by fluorescent X-ray analysis and ICP (Inductively Coupled Plasma) analysis. As a result, chemical formula (BiGdYb) _2.996 Na _0.004 Fe _4.993 Ge _0.007 O ₁₂ was obtained. Therefore, the light loss of the Faraday rotator is reduced when an element that is stable in tetravalence in the garnet, such as Ge, enters the garnet single crystal. In particular, when the amount of Ge in the garnet single crystal is 0.007 in the chemical formula. It has been found that the optical loss of the Faraday rotator can be minimized. Even if the amount of Ge in the garnet single crystal is further increased, the optical loss of the Faraday rotator remains at the minimum value.

Ｇｅ以外のＳｉ、Ｔｉ及びＰｔなどのガーネット中で４価が安定な元素についても、上記と同様の条件でファラデー回転子の光損失を低減できることが分かった。また、Ｇｅ、Ｓｉ、Ｔｉ及びＰｔのうち２種以上を組み合わせて用いても、上記と同様の条件でファラデー回転子の光損失を低減できることが分かった。すなわち、Ｎａ、Ｆｅ及びＭ２（Ｍ２はＳｉ、Ｇｅ、Ｔｉ、Ｐｔから選択される少なくとも１種類以上の元素）を含む配合材料から育成したガーネット単結晶を用いることにより、低損失のファラデー回転子が得られる。さらに、Ｍ２のＦｅに対するモル比（Ｍ２／Ｆｅモル比）が０．００４以上である配合材料から育成したガーネット単結晶を用いることにより、さらに低損失のファラデー回転子が得られる。 It has been found that the optical loss of the Faraday rotator can be reduced under the same conditions as described above even for elements that are stable in tetravalence in garnets such as Si, Ti, and Pt other than Ge. It was also found that the optical loss of the Faraday rotator can be reduced under the same conditions as described above even when two or more of Ge, Si, Ti and Pt are used in combination. That is, by using a garnet single crystal grown from a compound material containing Na, Fe and M2 (M2 is at least one element selected from Si, Ge, Ti, and Pt), a low-loss Faraday rotator can be obtained. can get. Further, by using a garnet single crystal grown from a blended material having a molar ratio of M2 to Fe (M2 / Fe molar ratio) of 0.004 or more, a further low-loss Faraday rotator can be obtained.

Ｓｉ、Ｇｅ、Ｔｉ及びＰｔなどのガーネット中で４価が安定な元素と、２価の状態でガーネット中に入るＰｂとで電荷補償させて光損失を低減する技術は、従来から知られている（例えば、特許文献１乃至３参照）。しかし、ＰｂとＳｉ、Ｇｅ、Ｔｉ及びＰｔから選択される少なくとも１種の元素とで電荷補償させたガーネット単結晶から作製されるファラデー回転子の光損失は０．０１〜０．０５ｄＢ程度である。それに対し、ＮａとＳｉ、Ｇｅ、Ｔｉ及びＰｔから選択される少なくとも１種の元素とで電荷補償させたガーネット単結晶から得られるファラデー回転子の損失は０〜０．０１ｄＢである。したがって本実施の形態によれば、Ｐｂを含む従来のファラデー回転子よりもさらに低損失で優れた特性が得られることが分かった。これは、ＮａとＳｉ、Ｇｅ、Ｔｉ及びＰｔとの組合せの方が完全に電荷を補償できるためと考えられる。 A technique for reducing optical loss by charge compensation by using a tetravalent stable element in a garnet such as Si, Ge, Ti and Pt and Pb entering the garnet in a divalent state has been known. (For example, see Patent Documents 1 to 3). However, the optical loss of a Faraday rotator manufactured from a garnet single crystal that is charge-compensated with Pb and at least one element selected from Si, Ge, Ti, and Pt is about 0.01 to 0.05 dB. . On the other hand, the loss of the Faraday rotator obtained from the garnet single crystal in which charge is compensated with Na and at least one element selected from Si, Ge, Ti and Pt is 0 to 0.01 dB. Therefore, according to the present embodiment, it has been found that excellent characteristics can be obtained with lower loss than the conventional Faraday rotator including Pb. This is presumably because the combination of Na and Si, Ge, Ti and Pt can fully compensate the charge.

Ｓｉ、Ｇｅ、Ｔｉ及びＰｔが所定量以上ガーネット単結晶中に入り電荷のバランスが崩れると、電荷を補償するようにＮａがガーネット中に入る。そのためＳｉ、Ｇｅ、Ｔｉ及びＰｔでＦｅを多量に置換した場合でも、Ｎａがガーネットに入ることで電荷は補償される。しかしながら、磁性ガーネット単結晶においてＳｉ、Ｇｅ、Ｔｉ及びＰｔの置換量が１．６より大きくなると、キュリー点が室温付近まで低下するためファラデー回転子としての使用が困難になる。したがって、Ｓｉ、Ｇｅ、Ｔｉ及びＰｔの置換量の上限は化学式で１．６となる。４価が安定な元素と１価が安定な元素とが１：２の比率でガーネット単結晶に入れば電荷のバランスをとることができるため、ガーネット単結晶にＳｉ、Ｇｅ、Ｔｉ及びＰｔが化学式で１．６だけ入るとき、Ｎａは化学式で０．８だけ入る。すなわち、ファラデー回転子に使用可能な磁性ガーネット単結晶に含まれるＮａの上限は化学式で０．８となる。 When Si, Ge, Ti, and Pt enter the garnet single crystal in a predetermined amount or more and the balance of charges is lost, Na enters the garnet so as to compensate for the charges. Therefore, even when a large amount of Fe is substituted with Si, Ge, Ti, and Pt, the charge is compensated by Na entering the garnet. However, when the substitution amount of Si, Ge, Ti, and Pt is larger than 1.6 in the magnetic garnet single crystal, the Curie point is lowered to near room temperature, so that it is difficult to use as a Faraday rotator. Therefore, the upper limit of the substitution amount of Si, Ge, Ti and Pt is 1.6 in the chemical formula. Since the charge balance can be achieved if the tetravalent stable element and the monovalent stable element enter the garnet single crystal in a ratio of 1: 2, Si, Ge, Ti and Pt are represented by the chemical formula in the garnet single crystal. Na enters only 0.8 in the chemical formula. That is, the upper limit of Na contained in the magnetic garnet single crystal usable for the Faraday rotator is 0.8 in the chemical formula.

Ｎａを含む溶媒で磁性ガーネット単結晶を育成する場合には、Ｎａを含まない溶媒に比して溶液の過飽和状態をより安定に保つことができる。そのためＢｉは、化学式で２．０程度まで安定してガーネット単結晶に入ることができる。一方、ファラデー回転子として十分な回転係数（ｄｅｇ／μｍ）を得るためには、Ｂｉは化学式で０．５以上は必要である。 When a magnetic garnet single crystal is grown with a solvent containing Na, the supersaturated state of the solution can be kept more stable than a solvent containing no Na. Therefore, Bi can enter the garnet single crystal stably up to about 2.0 in chemical formula. On the other hand, in order to obtain a sufficient rotation coefficient (deg / μm) as a Faraday rotator, Bi must be 0.5 or more in chemical formula.

また本実施の形態では、磁性ガーネット単結晶に含まれる希土類元素として、単独又は組合せにより安定してＦｅとガーネット単結晶を作ることができるイットリウム（Ｙ）、ランタン（Ｌａ）、セリウム（Ｃｅ）、プラセオジム（Ｐｒ）、ネオジム（Ｎｄ）、サマリウム（Ｓｍ）、ユウロピウム（Ｅｕ）、ガドリニウム（Ｇｄ）、テルビウム（Ｔｂ）、ジスプロシウム（Ｄｙ）、ホルミウム（Ｈｏ）、エルビウム（Ｅｒ）、ツリウム（Ｔｍ）、イッテルビウム（Ｙｂ）及びルテチウム（Ｌｕ）が用いられる。 In the present embodiment, as the rare earth element contained in the magnetic garnet single crystal, yttrium (Y), lanthanum (La), cerium (Ce), which can stably form Fe and garnet single crystals alone or in combination, Praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), Ytterbium (Yb) and lutetium (Lu) are used.

以上説明したように、本実施の形態による磁性ガーネット単結晶は、化学式Ｂｉ_αＮａ_βＭ１_{３−α−β}Ｆｅ_5-γＭ２_γＯ_１２（Ｍ１はＹ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕから選択される少なくとも１種類以上の元素、Ｍ２はＳｉ、Ｇｅ、Ｔｉ、Ｐｔから選択される少なくとも１種類以上の元素であり、０．５＜α≦２．０、０＜β≦０．８、０．２≦３−α−β＜２．５、０＜γ≦１．６）で表される。本実施の形態によれば、Ｐｂをほぼ完全に除去した磁性ガーネット単結晶及びそれを用いた光学素子を実現できる。また本実施の形態によれば、光学素子の光損失を低減できる。
以下、本実施の形態による磁性ガーネット単結晶及びその製造方法並びにそれを用いた光学素子について、実施例及び比較例を用いてより具体的に説明する。 As described above, the magnetic garnet single crystal according to this embodiment, the chemical formula _{_{_{Bi α Na β M1 3-α}}} -β Fe 5-γ M2 γ O 12 (M1 is Y, La, Ce, Pr, Nd, Sm , Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, M2 is at least one element selected from Si, Ge, Ti, Pt 0.5 <α ≦ 2.0, 0 <β ≦ 0.8, 0.2 ≦ 3-α−β <2.5, 0 <γ ≦ 1.6). According to the present embodiment, a magnetic garnet single crystal from which Pb is almost completely removed and an optical element using the same can be realized. Moreover, according to this Embodiment, the optical loss of an optical element can be reduced.
Hereinafter, the magnetic garnet single crystal according to the present embodiment, the manufacturing method thereof, and the optical element using the same will be described more specifically with reference to Examples and Comparative Examples.

（実施例１−１）
図１は、磁性ガーネット単結晶育成工程の一部を示している。まず、金（Ａｕ）製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ／Ｆｅモル比を０．００６とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。融液８から磁性ガーネット単結晶膜を育成するための基板には、引き上げ法により育成したガーネット単結晶のインゴットから作製された単結晶ウエハを用いる。本実施例では単結晶育成用基板１０として、ＣａＭｇＺｒ置換ＧＧＧ（ガドリニウム・ガリウム・ガーネット）単結晶基板（（ＧｄＣａ）_３（ＧａＭｇＺｒ）_５Ｏ_１２）を用いている。 (Example 1-1)
FIG. 1 shows a part of the magnetic garnet single crystal growing step. First, a crucible 4 made of gold (Au) was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. . At this time, the molar ratio of Ge / Fe was set to 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. As a substrate for growing a magnetic garnet single crystal film from the melt 8, a single crystal wafer made from a garnet single crystal ingot grown by a pulling method is used. In this embodiment, a CaMgZr-substituted GGG (gadolinium gallium garnet) single crystal substrate ((GdCa) ₃ (GaMgZr) ₅ O ₁₂ ) is used as the single crystal growth substrate 10.

ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{４．９９０}Ｇｅ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＧｅ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The single crystal film 12 was grown was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.300 Gd 1.200 Yb 0.500 Fe 4.990}}}} Ge 0.010 O 12, Na could be detected . Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal film 12 was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FeGe). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例１−２）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ／Ｆｅモル比を０．００４とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{４．９９３}Ｇｅ_{０．００７}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９６}Ｎａ_{０．００４}（ＦｅＧｅ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 1-2)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge / Fe was set to 0.004. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The single crystal film 12 was grown was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.300 Gd 1.200 Yb 0.500 Fe 4.993}}}} Ge 0.007 O 12, Na could be detected . Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, it was found that the chemical formula of the magnetic garnet single crystal film 12 was (BiGdYb) _2.996 Na _0.004 (FeGe) _5.000 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例１−３）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ／Ｆｅモル比を０．００８とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところＮａが検出され、組成はＢｉ_{１．２９３}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｎａ_{０．００７}Ｆｅ_{４．９８７}Ｇｅ_{０．０１３}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 1-3)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge / Fe was set to 0.008. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The composition of the grown single crystal film 12 was analyzed by fluorescent X-ray analysis. As a result, Na was detected, and the composition was Bi _1.293 Gd _1.200 Yb _0.500 Na _0.007 Fe _4.987 Ge _0.013 O ₁₂ . there were. The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例１−４）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ／Ｆｅモル比を０．０１２とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．２９０}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｎａ_{０．０１０}Ｆｅ_{４．９８０}Ｇｅ_{０．０２０}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 1-4)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. The Ge / Fe molar ratio at this time was set to 0.012. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. When the composition of the grown single crystal film 12 was analyzed by fluorescent X-ray analysis, the composition was Bi _1.290 Gd _1.200 Yb _0.500 Na _0.010 Fe _4.980 Ge _0.020 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例１−５）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ／Ｆｅモル比を０．０２０とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．２８３}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｎａ_{０．０１７}Ｆｅ_{４．９６７}Ｇｅ_{０．０３３}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 1-5)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge / Fe was set to 0.020. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The composition of the grown single crystal film 12 was analyzed by fluorescent X-ray analysis. As a result, the composition was Bi _1.283 Gd _1.200 Yb _0.500 Na _0.017 Fe _4.967 Ge _0.033 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例１−６）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ／Ｆｅモル比を０．００２とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{４．９９７}Ｇｅ_{０．００３}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９８}Ｎａ_{０．００２}（ＦｅＧｅ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０．２〜０．２５ｄＢであった。 (Example 1-6)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge / Fe was set to 0.002. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The single crystal film 12 was grown was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.300 Gd 1.200 Yb 0.500 Fe 4.997}}}} Ge 0.003 O 12, Na could be detected . Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, it was found that the chemical formula of the magnetic garnet single crystal film 12 was (BiGdYb) _2.998 Na _0.002 (FeGe) _5.000 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0.2 to 0.25 dB.

（実施例１−７）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ／Ｆｅモル比を０．００３とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{４．９９４}Ｇｅ_{０．００６}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９７}Ｎａ_{０．００３}（ＦｅＧｅ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０．０４〜０．０７ｄＢであった。 (Example 1-7)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge / Fe was set to 0.003. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The single crystal film 12 was grown was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.300 Gd 1.200 Yb 0.500 Fe 4.994}}}} Ge 0.006 O 12, Na could be detected . Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, it was found that the chemical formula of the magnetic garnet single crystal film 12 was (BiGdYb) _2.997 Na _0.003 (FeGe) _5.000 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0.04 to 0.07 dB.

（実施例１−８）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＳｉ／Ｆｅモル比を０．００６とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{４．９９０}Ｓｉ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＳｉ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 1-8)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. The Si / Fe molar ratio at this time was 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The single crystal film 12 was grown was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.300 Gd 1.200 Yb 0.500 Fe 4.990}}}} Si 0.010 O 12, Na could be detected . Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal film 12 was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FeSi). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例１−９）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＴｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＴｉ／Ｆｅモル比を０．００６とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{４．９９０}Ｔｉ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＴｉ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 1-9)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. The Ti / Fe molar ratio at this time was 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The single crystal film 12 was grown was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.300 Gd 1.200 Yb 0.500 Fe 4.990}}}} Ti 0.010 O 12, Na could be detected . Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal film 12 was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FeTi). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例１−１０）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＰｔＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＰｔ／Ｆｅモル比を０．００６とした。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{４．９９０}Ｐｔ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＰｔ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 1-10)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , PtO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. The Pt / Fe molar ratio at this time was 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. The single crystal film 12 was grown was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.300 Gd 1.200 Yb 0.500 Fe 4.990}}}} Pt 0.010 O 12, Na could be detected . Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal film 12 was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FePt). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（比較例１−１）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶膜１２を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．３００}Ｇｄ_{１．２００}Ｙｂ_{０．５００}Ｆｅ_{５．０００}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９８}Ｎａ_{０．００２}Ｆｅ_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は３．０〜３．５ｄＢであり、極めて高損失であった。 (Comparative Example 1-1)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. When the composition of the grown single crystal film 12 was analyzed by fluorescent X-ray analysis, the composition was Bi _1.300 Gd _1.200 Yb _0.500 Fe _5.000 O ₁₂ and Na could not be detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, it was found that the chemical formula of the magnetic garnet single crystal was (BiGdYb) _2.998 Na _0.002 Fe _5.000 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 3.0 to 3.5 dB, which was extremely high loss.

図２は、上記の実施例及び比較例について、配合材料のＭ２／Ｆｅモル比、育成したガーネット単結晶のＮａ量β及びＭ２量γ、並びに作製したファラデー回転子の光損失（ｄＢ）をまとめて示している。図２に示すように、Ｎａ及びＭ２を含む磁性ガーネット単結晶を用いたファラデー回転子（実施例１−１乃至１−１０）では、Ｎａを含みＭ２を含まない磁性ガーネット単結晶を用いたファラデー回転子（比較例１−１）よりも光損失を低減できることが分かる。特に、磁性ガーネット単結晶のＭ２量γが０．００７以上である場合（実施例１−１乃至１−５及び１−８乃至１−１０）、Ｐｂを含む溶媒から育成した磁性ガーネット単結晶を用いて作製した従来のファラデー回転子（例えば光損失０．０５ｄＢ以下）と比較しても極めて低損失のファラデー回転子が得られる。 FIG. 2 summarizes the M2 / Fe molar ratio of the blended material, the Na amount β and M2 amount γ of the grown garnet single crystal, and the optical loss (dB) of the manufactured Faraday rotator for the above Examples and Comparative Examples. It shows. As shown in FIG. 2, in the Faraday rotator (Examples 1-1 to 1-10) using the magnetic garnet single crystal containing Na and M2, the Faraday using the magnetic garnet single crystal containing Na and not containing M2. It can be seen that the optical loss can be reduced as compared with the rotor (Comparative Example 1-1). In particular, when the M2 amount γ of the magnetic garnet single crystal is 0.007 or more (Examples 1-1 to 1-5 and 1-8 to 1-10), the magnetic garnet single crystal grown from the solvent containing Pb is used. Even when compared with a conventional Faraday rotator (for example, an optical loss of 0.05 dB or less) manufactured by using the same, a very low loss Faraday rotator can be obtained.

また、Ｎａ、Ｆｅ、Ｍ１及びＭ２を含む材料から育成した磁性ガーネット単結晶を用いることによって、低損失のファラデー回転子が得られることが分かる。特に、Ｍ２／Ｆｅモル比が０．００４以上である場合には、極めて低損失のファラデー回転子が得られる。 It can also be seen that a low-loss Faraday rotator can be obtained by using a magnetic garnet single crystal grown from a material containing Na, Fe, M1, and M2. In particular, when the M2 / Fe molar ratio is 0.004 or more, a very low loss Faraday rotator can be obtained.

〔第２の実施の形態〕
本発明の第２の実施の形態による磁性ガーネット単結晶及びその製造方法並びにそれを用いた光学素子について図１及び図３を用いて説明する。Ｎａは希土類やＢｉと比べてイオン半径が大きな元素であり、ガーネットの結晶構造で希土類、Ｂｉと同じサイトを占める。ガーネット膜の育成では単結晶割れを防ぐため、基板と膜の格子定数をほぼ同じにする必要がある。そこでＮａがガーネット中に入った場合に格子定数を一定の値に維持するため、ＢｉやＧｄ、Ｔｂなどの比較的大きなイオン半径を持つ元素の量を減らし、Ｙｂ、Ｈｏ、Ｙなどの比較的小さなイオン半径を持つ元素を増やす必要が出てくる。Ｂｉは回転子の厚さに大きな影響を与え、ＧｄやＴｂなどは回転子の飽和磁界に影響を与える。そこでガーネット中のＮａ量が増えると格子定数を一定に保つため、希土類、Ｂｉの組成が変わることになり、飽和磁界や厚さなどの回転子の特性がＰｂを含有する従来の回転子と異なってくる。Ｐｂ含有の従来回転子は同じ特性を持つ非鉛回転子で代替することが望ましい。そのためにはＮａ量βは少ない方が好ましく、実用的には少なくとも０．１以下とすることが必要となる。さらに非鉛の回転子の特性を従来の回転子に同等まで近づけるにはＮａ量βは０．０５以下とすることがさらに望ましい。また、Ｓｉ、Ｇｅ、Ｔｉの中でもＳｉはイオン半径の小さな元素であり、Ｓｉをガーネットに加えると大きなイオン半径を持つＮａがガーネットに入る効果を緩和する効果がある。そのためＳｉをガーネット中に添加して電荷補償することが望ましい。ＰｔはＳｉ、Ｇｅ、Ｔｉと同じく４価が安定な陽イオンの状態でガーネット中のＮａと電荷補償し光吸収を抑制する効果がある。しかし、Ｐｔは安定な複合酸化物を作りやすい元素であり、Ｐｔ量δが０．１６より大きいガーネット膜の育成を試みると、ガーネット膜の育成と同時に溶液中でＰｔを含有する複合酸化物の析出が起き、溶液の過飽和状態を安定に維持できなくなる。そのためファラデー回転子の作製に必要な厚さ数百μｍで結晶欠陥の少ないガーネット膜を育成することは困難となる。従って、Ｐｔ量δは０．１６より小さいことが望ましい。
以下、本実施の形態による磁性ガーネット単結晶及びその製造方法並びにそれを用いた光学素子について、実施例及び比較例を用いてより具体的に説明する。 [Second Embodiment]
A magnetic garnet single crystal according to a second embodiment of the present invention, a manufacturing method thereof, and an optical element using the same will be described with reference to FIGS. Na is an element having a larger ionic radius than rare earth and Bi, and occupies the same site as rare earth and Bi in the crystal structure of garnet. In growing a garnet film, the lattice constant of the substrate and the film must be substantially the same in order to prevent single crystal cracking. Therefore, in order to maintain a constant lattice constant when Na enters the garnet, the amount of elements having a relatively large ionic radius such as Bi, Gd, and Tb is reduced, and Yb, Ho, Y, etc. It is necessary to increase the number of elements with a small ion radius. Bi greatly affects the thickness of the rotor, and Gd, Tb, and the like affect the saturation magnetic field of the rotor. Therefore, as the amount of Na in the garnet increases, the composition of the rare earth and Bi changes to keep the lattice constant constant, and the rotor characteristics such as saturation magnetic field and thickness are different from those of conventional rotors containing Pb. Come. It is desirable to replace the conventional rotor containing Pb with a lead-free rotor having the same characteristics. For this purpose, it is preferable that the amount of Na is small, and it is necessary to set it to practically at least 0.1 or less. Further, in order to bring the characteristics of the lead-free rotor to the same level as that of a conventional rotor, the Na amount β is more preferably 0.05 or less. Further, among Si, Ge, and Ti, Si is an element having a small ion radius, and adding Si to the garnet has an effect of alleviating the effect of Na having a large ion radius entering the garnet. Therefore, it is desirable to compensate the charge by adding Si into the garnet. Pt, like Si, Ge, and Ti, has an effect of suppressing light absorption by charge-compensating with Na in garnet in the state of a tetravalent stable cation. However, Pt is an element that makes it easy to form a stable composite oxide. If an attempt is made to grow a garnet film having a Pt amount δ of greater than 0.16, the growth of the garnet film simultaneously with the growth of the composite oxide containing Pt in the solution. Precipitation occurs and the supersaturated state of the solution cannot be stably maintained. For this reason, it is difficult to grow a garnet film having a thickness of several hundred μm and few crystal defects necessary for manufacturing a Faraday rotator. Accordingly, the Pt amount δ is desirably smaller than 0.16.
Hereinafter, the magnetic garnet single crystal according to the present embodiment, the manufacturing method thereof, and the optical element using the same will be described more specifically with reference to Examples and Comparative Examples.

（実施例２−１）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．００６である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜１２が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．６１０}Ｙｂ_{０．３９０}Ｆｅ_{４．９９０}Ｇｅ_{０．００５}Ｓｉ_{０．００５}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶膜１２の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＧｅＳｉ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-1)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film 12 having a thickness of 500 μm was obtained. Composition analysis of the grown single crystal by X-ray fluorescence analysis revealed that the composition was Bi _1.000 Gd _1.610 Yb _0.390 Fe _4.990 Ge _0.005 Si _0.005 O ₁₂ and Na could not be detected. There wasn't. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal film 12 was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FeGeSi). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−２）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．００４である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．６１０}Ｙｂ_{０．３９０}（ＦｅＧｅＳｉ）_{５．０００}Ｏ_１２であり、ＧｅとＳｉ量は確定できずＮａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９６}Ｎａ_{０．００４}Ｆｅ_{４．９９３}Ｇｅ_{０．００４}Ｓｉ_{０．００３}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-2)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.004. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. The composition of the grown single crystal was analyzed by fluorescent X-ray analysis. The composition was Bi _1.000 Gd _1.610 Yb _0.390 (FeGeSi) _5.000 O ₁₂ , and the amounts of Ge and Si could not be determined. It was not detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, it was found that the chemical formula of the magnetic garnet single crystal was (BiGdYb) _2.996 Na _0.004 Fe _4.993 Ge _0.004 Si _0.003 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−３）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．００８である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところＮａが検出され、組成はＢｉ_{０．９９０}Ｇｄ_{１．６１０}Ｙｂ_{０．３９３}Ｎａ_{０．００７}Ｆｅ_{４．９８７}Ｇｅ_{０．００８}Ｓｉ_{０．００５}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１３μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-3)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.008. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. When the grown single crystal was subjected to composition analysis by fluorescent X-ray analysis, Na was detected, and the composition was Bi _0.990 Gd _1.610 Yb _0.393 Na _0.007 Fe _4.987 Ge _0.008 Si _0.005 O. It was ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 413 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−４）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．０１２である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{０．９８６}Ｇｄ_{１．６１０}Ｙｂ_{０．３９４}Ｎａ_{０．０１０}Ｆｅ_{４．９８０}Ｇｅ_{０．０１５}Ｓｉ_{０．００５}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１５μｍ、１ｍｍ角の形状での飽和磁界は６１７Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-4)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.012. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. The composition of the grown single crystal was analyzed by fluorescent X-ray analysis, and the composition was Bi _0.986 Gd _1.610 Yb _0.394 Na _0.010 Fe _4.980 Ge _0.015 Si _0.005 O ₁₂ . . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 415 μm, and the saturation magnetic field in a 1 mm square shape was 617 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−５）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．０２０である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{０．９９０}Ｇｄ_{１．５９０}Ｙｂ_{０．４０３}Ｎａ_{０．０１７}Ｆｅ_{４．９６７}Ｇｅ_{０．０２８}Ｓｉ_{０．００５}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１３μｍ、１ｍｍ角の形状での飽和磁界は６２６Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-5)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.020. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. The composition of the grown single crystal was analyzed by fluorescent X-ray analysis, and the composition was Bi _0.990 Gd _1.590 Yb _0.403 Na _0.017 Fe _4.967 Ge _0.028 Si _0.005 O ₁₂ . . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 413 μm, and the saturation magnetic field in a 1 mm square shape was 626 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−６）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．０６０である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{９．５００}Ｇｄ_{１．５８０}Ｙｂ_{０．４２０}Ｎａ_{０．０５０}Ｆｅ_{４．９００}Ｇｅ_{０．０８０}Ｓｉ_{０．０２０}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４３１μｍ、１ｍｍ角の形状での飽和磁界は６３１Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-6)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.060. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. The composition of the grown single crystal was analyzed by X-ray fluorescence analysis, and the composition was Bi _9.500 Gd _1.580 Yb _0.420 Na _0.050 Fe _4.900 Ge _0.080 Si _0.020 O ₁₂ . . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 431 μm, and the saturation magnetic field in a 1 mm square shape was 631 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−７）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．１２０である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{０．９２３}Ｇｄ_{１．５１０}Ｙｂ_{０．４６７}Ｎａ_{０．１００}Ｆｅ_{４．８００}Ｇｅ_{０．１６０}Ｓｉ_{０．０４０}Ｏ_１２であった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４４３μｍ、１ｍｍ角の形状での飽和磁界は６６２Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-7)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.120. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. When the composition of the grown single crystal was analyzed by fluorescent X-ray analysis, the composition was Bi _0.923 Gd _1.510 Yb _0.467 Na _0.100 Fe _4.800 Ge _0.160 Si _0.040 O ₁₂ . . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 443 μm, and the saturation magnetic field in a 1 mm square shape was 662 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−８）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅ、ＳｉとＦｅのモル比（Ｇｅ＋Ｓｉ）／Ｆｅは０．００２である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．６１０}Ｙｂ_{０．３９０}（ＦｅＧｅＳｉ）_{５．０００}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９８}Ｎａ_{０．００２}Ｆｅ_{４．９９７}Ｇｅ_{０．００２}Ｓｉ_{０．００１}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０．２〜０．２５ｄＢであった。Ｇｅを添加しない回転子よりは低損失であった。 (Example 2-8)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio of Ge, Si and Fe (Ge + Si) / Fe is 0.002. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. Composition analysis of the grown single crystal by fluorescent X-ray analysis revealed that the composition was Bi _1.000 Gd _1.610 Yb _0.390 (FeGeSi) _5.000 O ₁₂ and Na could not be detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, it was found that the chemical formula of the magnetic garnet single crystal was (BiGdYb) _2.998 Na _0.002 Fe _4.997 Ge _0.002 Si _0.001 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0.2 to 0.25 dB. The loss was lower than that of the rotor without adding Ge.

（実施例２−９）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＳｉとＦｅのモル比Ｓｉ／Ｆｅは０．００６である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．５２０}Ｙｂ_{０．４８０}Ｆｅ_{４．９９０}Ｓｉ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＳｉ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-9)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio Si / Fe between Si and Fe is 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. Was grown single crystal was compositionally analyzed by X-ray fluorescence analysis, the composition is a _{_{_{_{Bi 1.000 Gd 1.520 Yb 0.480 Fe 4.990}}}} Si 0.010 O 12, Na could be detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FeSi). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−１０）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＧｅＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＧｅとＦｅのモル比Ｇｅ／Ｆｅは０．００６である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．６１０}Ｙｂ_{０．３９０}Ｆｅ_{４．９９０}Ｇｅ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＧｅ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-10)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , GeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio Ge / Fe of Ge and Fe is 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. Composition analysis of the grown single crystal by fluorescent X-ray analysis revealed that the composition was Bi _1.000 Gd _1.610 Yb _0.390 Fe _4.990 Ge _0.010 O ₁₂ and Na could not be detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FeGe). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−１１）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＴｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＴｉとＦｅのモル比Ｔｉ／Ｆｅは０．００６である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．６１０}Ｙｂ_{０．３９０}Ｆｅ_{４．９９０}Ｔｉ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＴｉ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-11)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio Ti / Fe of Ti and Fe is 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. Composition analysis of the grown single crystal by fluorescent X-ray analysis revealed that the composition was Bi _1.000 Gd _1.610 Yb _0.390 Fe _4.990 Ti _0.010 O ₁₂ and Na could not be detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FeTi). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（実施例２−１２）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＰｔＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＰｔとＦｅのモル比Ｐｔ／Ｆｅは０．００６である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．６１０}Ｙｂ_{０．３９０}Ｆｅ_{４．９９０}Ｐｔ_{０．０１０}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９５}Ｎａ_{０．００５}（ＦｅＰｔ）_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は０〜０．０１ｄＢであり、極めて低損失であった。 (Example 2-12)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , PtO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio Pt / Fe of Pt and Fe is 0.006. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. Composition analysis of the grown single crystal by fluorescent X-ray analysis revealed that the composition was Bi _1.000 Gd _1.610 Yb _0.390 Fe _4.990 Pt _0.010 O ₁₂ and Na could not be detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, the chemical formula of the magnetic garnet single crystal was found to be _{_{_{_{5.000 O 12 (BiGdYb) 2.995 Na}}}} 0.005 (FePt). The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 0 to 0.01 dB, which was extremely low loss.

（比較例２−１）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。膜厚５００μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{１．０００}Ｇｄ_{１．６１０}Ｙｂ_{０．３９０}Ｆｅ_{５．０００}Ｏ_１２であり、Ｎａは検出できなかった。次にＩＣＰ分析法で詳しく組成を評価したところ、Ｎａの含有量を確定できた。その結果、磁性ガーネット単結晶の化学式は（ＢｉＧｄＹｂ）_{２．９９８}Ｎａ_{０．００２}Ｆｅ_{５．０００}Ｏ_１２であることが分かった。育成した単結晶膜１２を加工して、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板を作製した。その単結晶板の研磨面に無反射コートを成膜し、ファラデー回転子を作製した。回転子の厚さは４１０μｍ、１ｍｍ角の形状での飽和磁界は６１８Ｏｅであった。作製したファラデー回転子から２０個抜き取り、波長１．５５μｍの光に対する光損失を評価した。ファラデー回転子の光損失は３．０〜３．５ｄＢであり、極めて高損失であった。 (Comparative Example 2-1)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a thickness of 500 μm was obtained. The composition of the grown single crystal was analyzed by fluorescent X-ray analysis. As a result, the composition was Bi _1.000 Gd _1.610 Yb _0.390 Fe _5.000 O ₁₂ , and Na could not be detected. Next, when the composition was evaluated in detail by ICP analysis, the content of Na could be determined. As a result, it was found that the chemical formula of the magnetic garnet single crystal was (BiGdYb) _2.998 Na _0.002 Fe _5.000 O ₁₂ . The grown single crystal film 12 was processed to produce a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm. A non-reflective coating was formed on the polished surface of the single crystal plate to produce a Faraday rotator. The thickness of the rotor was 410 μm, and the saturation magnetic field in a 1 mm square shape was 618 Oe. Twenty pieces were extracted from the prepared Faraday rotator and evaluated for light loss with respect to light having a wavelength of 1.55 μm. The optical loss of the Faraday rotator was 3.0 to 3.5 dB, which was extremely high loss.

（比較例２−２）
Ａｕ製のルツボ４にＧｄ_２Ｏ_３、Ｙｂ_２Ｏ_３、Ｆｅ_２Ｏ_３、ＰｔＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３、ＮａＯＨを充填して、電気炉に配置した。このときのＰｔとＦｅのモル比Ｐｔ／Ｆｅは０．１００である。９５０℃まで炉温を上げてルツボ４内の材料を溶解して融液８を生成し、Ａｕ製の攪拌用冶具を使用して融液８を攪拌した。ＣａＭｇＺｒ置換ＧＧＧ基板１０をＡｕ製の固定冶具２に取り付けて炉内に投入し、８５０℃まで炉温を下げてから基板１０の片面を融液８に接触させてエピタキシャル成長を４０時間行った。育成した表面に多数の結晶欠陥のある膜厚３６５μｍの磁性ガーネット単結晶膜が得られた。育成した単結晶を蛍光Ｘ線分析により組成分析したところ、組成はＢｉ_{０．９５０}Ｇｄ_{１．５９０}Ｙｂ_{０．３８０}Ｎａ_{０．０８０}Ｆｅ_{４．８４０}Ｐｔ_{０．１６０}Ｏ_１２であった。単結晶膜の厚さが不足したため、波長１．５５μｍの光に対して回転角４５ｄｅｇとなる単結晶板は作製できなかった。 (Comparative Example 2-2)
A crucible 4 made of Au was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , PtO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and NaOH and placed in an electric furnace. At this time, the molar ratio Pt / Fe of Pt and Fe is 0.100. The furnace temperature was raised to 950 ° C. to dissolve the material in the crucible 4 to produce a melt 8, and the melt 8 was stirred using a stirring jig made of Au. The CaMgZr-substituted GGG substrate 10 was attached to the Au fixing jig 2 and placed in the furnace. After the furnace temperature was lowered to 850 ° C., one side of the substrate 10 was brought into contact with the melt 8 and epitaxial growth was performed for 40 hours. A magnetic garnet single crystal film having a film thickness of 365 μm having many crystal defects on the grown surface was obtained. The composition of the grown single crystal was analyzed by fluorescent X-ray analysis. As a result, the composition was Bi _0.950 Gd _1.590 Yb _0.380 Na _0.080 Fe _4.840 Pt _0.160 O ₁₂ . Since the thickness of the single crystal film was insufficient, a single crystal plate having a rotation angle of 45 deg with respect to light having a wavelength of 1.55 μm could not be produced.

図３は、上記の実施例及び比較例について、配合材料の（Ｍ２＋Ｍ３）／Ｆｅモル比、育成したガーネット単結晶のＮａ量β、Ｍ２量γ、及びＭ３量δ、並びに作製したファラデー回転子の光損失（ｄＢ）をまとめて示している。図３に示すように、Ｎａ、Ｍ２及びＭ３を含む磁性ガーネット単結晶を用いたファラデー回転子（実施例２−１乃至２−１２）では、Ｍ２及びＭ３を含まない磁性ガーネット単結晶を用いたファラデー回転子（比較例２−１）よりも光損失を低減できることが分かる。特に、磁性ガーネット単結晶のＮａ量βが０．１以下であってＧｅ及びＳｉからなるＭ２量γ（Ｍ３量δ＝０）が０．２以下である場合（実施例２−１乃至２−８）、好ましくはＮａ量βが０．０５以下であって、Ｍ２量γ（Ｍ３量δ＝０）が０．１以下である場合（実施例２−１乃至２−６及び２−８）極めて低損失のファラデー回転子が得られる。 FIG. 3 shows the (M2 + M3) / Fe molar ratio of the blended material, the Na amount β, the M2 amount γ, and the M3 amount δ of the grown garnet single crystal, and the prepared Faraday rotator for the above Examples and Comparative Examples. The optical loss (dB) is shown together. As shown in FIG. 3, in the Faraday rotator (Examples 2-1 to 2-12) using the magnetic garnet single crystal containing Na, M2, and M3, the magnetic garnet single crystal not containing M2 and M3 was used. It can be seen that the optical loss can be reduced as compared with the Faraday rotator (Comparative Example 2-1). In particular, when the Na amount β of the magnetic garnet single crystal is 0.1 or less and the M2 amount γ (M3 amount δ = 0) made of Ge and Si is 0.2 or less (Examples 2-1 to 2- 8) Preferably, when Na amount β is 0.05 or less and M2 amount γ (M3 amount δ = 0) is 0.1 or less (Examples 2-1 to 2-6 and 2-8) An extremely low loss Faraday rotator is obtained.

単結晶育成工程の一部を示す図である。It is a figure which shows a part of single crystal growth process. 本発明の第１の実施の形態の実施例１−１乃至１−１０及び比較例１−１のＭ２／Ｆｅモル比、Ｎａ量β、Ｍ２量γ、及び光損失をまとめて示す表である。It is a table | surface which shows collectively the M2 / Fe molar ratio, Na amount (beta), M2 amount (gamma), and optical loss of Example 1-1 thru | or 1-10 of the 1st Embodiment of this invention, and Comparative Example 1-1. . 本発明の第２の実施の形態の実施例２−１乃至２−１２及び比較例２−１及び２−２の（Ｍ２＋Ｍ３）／Ｆｅモル比、Ｎａ量β、（Ｍ２＋Ｍ３）量（γ＋δ）、及び光損失をまとめて示す表である。(M2 + M3) / Fe molar ratio, Na amount β, (M2 + M3) amount (γ + δ) of Examples 2-1 to 2-12 and Comparative Examples 2-1 and 2-2 of the second embodiment of the present invention, It is a table | surface which shows and optical loss collectively.

符号の説明Explanation of symbols

２固定冶具
４ルツボ
８融液
１０基板
１２単結晶膜 2 Fixing jig 4 Crucible 8 Melt 10 Substrate 12 Single crystal film

Claims

化学式Ｂｉ_αＮａ_βＭ１_{３−α−β}Ｆｅ_5-γＭ２_γＯ_１２（Ｍ１はＹ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕから選択される少なくとも１種類以上の元素、Ｍ２はＳｉ、Ｇｅ、Ｔｉから選択される少なくとも１種類以上の元素であり、０．５＜α≦２．０、０＜β≦０．８、０．２≦３−α−β＜２．５、０＜γ≦１．６）
で示されること
を特徴とする磁性ガーネット単結晶。 Formula _{_{_{Bi α Na β M1 3-α}}} -β Fe 5-γ M2 γ O 12 (M1 is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, At least one element selected from Lu, M2 is at least one element selected from Si, Ge, Ti, 0.5 <α ≦ 2.0, 0 <β ≦ 0.8, 0.2 ≦ 3-α−β <2.5, 0 <γ ≦ 1.6)
A magnetic garnet single crystal characterized by the following:

請求項１記載の磁性ガーネット単結晶であって、
前記γは、０．００７≦γ≦１．６であること
を特徴とする磁性ガーネット単結晶。 The magnetic garnet single crystal according to claim 1,
The magnetic garnet single crystal, wherein γ is 0.007 ≦ γ ≦ 1.6.

請求項１又は２に記載の磁性ガーネット単結晶を用いて作製されることを特徴とする光学素子。 An optical element manufactured using the magnetic garnet single crystal according to claim 1.

Ｎａ、Ｆｅ、Ｍ１及びＭ２（Ｍ１はＹ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕから選択される少なくとも１種類以上の元素、Ｍ２はＳｉ、Ｇｅ、Ｔｉから選択される少なくとも１種類以上の元素）を含む材料から融液を生成し、
前記融液を用いて磁性ガーネット単結晶を育成すること
を特徴とする磁性ガーネット単結晶の製造方法。 Na, Fe, M1 and M2 (M1 is at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, M2 generates a melt from a material containing at least one element selected from Si, Ge, and Ti,
A method for producing a magnetic garnet single crystal, comprising growing a magnetic garnet single crystal using the melt.

請求項４記載の磁性ガーネット単結晶の製造方法であって、
前記材料における前記Ｍ２のＦｅに対するモル比は、０．００４以上であること
を特徴とする磁性ガーネット単結晶の製造方法。 A method for producing a magnetic garnet single crystal according to claim 4,
The method for producing a magnetic garnet single crystal, wherein the molar ratio of M2 to Fe in the material is 0.004 or more.

請求項１記載の磁性ガーネット単結晶であって、
前記β及びγは、０＜β≦０．１、０＜γ≦０．２であること
を特徴とする磁性ガーネット単結晶。 The magnetic garnet single crystal according to claim 1,
Β and γ are 0 <β ≦ 0.1 and 0 <γ ≦ 0.2. A magnetic garnet single crystal.

請求項６記載の磁性ガーネット単結晶であって、
前記β及びγは、０＜β≦０．０５、０＜γ≦０．１であること
を特徴とする磁性ガーネット単結晶。 A magnetic garnet single crystal according to claim 6,
Β and γ are 0 <β ≦ 0.05 and 0 <γ ≦ 0.1. A magnetic garnet single crystal.

請求項６又は７に記載の磁性ガーネット単結晶であって、
前記Ｍ２は、少なくともＳｉを含む１種類以上の元素であること
を特徴とする磁性ガーネット単結晶。 The magnetic garnet single crystal according to claim 6 or 7,
The magnetic garnet single crystal, wherein M2 is one or more elements including at least Si.

化学式Ｂｉ_αＮａ_βＭ１_{３−α−β}Ｆｅ_5-γ-σＭ２_γＭ３_δＯ_１２（Ｍ１はＹ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕから選択される少なくとも１種類以上の元素、Ｍ２はＳｉ、Ｇｅ、Ｔｉから選択される少なくとも１種類以上の元素、Ｍ３はＰｔであり、０．５＜α≦２．０、０＜β≦０．８、０．２≦３−α−β＜２．５、０＜γ＋δ≦１．６、０≦γ＜１．６、０＜δ＜０．１６）
で示されること
を特徴とする磁性ガーネット単結晶。 Formula _{_{_{Bi α Na β M1 3-α}}} -β Fe 5-γ-σ M2 γ M3 δ O 12 (M1 is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one element selected from Tm, Yb, Lu, M2 is at least one element selected from Si, Ge, Ti, M3 is Pt, 0.5 <α ≦ 2.0, 0 <β ≦ 0.8, 0.2 ≦ 3-α−β <2.5, 0 <γ + δ ≦ 1.6, 0 ≦ γ <1.6, 0 <δ <0.16)
A magnetic garnet single crystal characterized by the following:

請求項１又は９に記載の磁性ガーネット単結晶から作製されることを特徴とするファラデー回転子。 A Faraday rotator produced from the magnetic garnet single crystal according to claim 1 or 9.