【作者】 杨雪；

【导师】 杨青慧；

【作者基本信息】 电子科技大学 ， 工程硕士（专业学位）， 2021， 硕士

【摘要】 迄今为止,液相外延（Liquid Phase Epitaxy,LPE）一直是制备单晶石榴石薄膜的最佳工艺之一。大量研究表明,利用LPE工艺,并选用Bi³⁺离子取代钇铁石榴石（YIG）中Y³⁺离子,可以生长出铋取代石榴石（Bi:YIG）薄膜。Bi:YIG薄膜的比法拉第旋角远大于纯YIG的比法拉第旋角,同时其易磁化轴也容易调控至面外取向,从而使其能够在较小的外加磁场下工作,进而满足磁光器件小型化和节能化的发展需求。因为Bi³⁺（108（?））的离子半径比Y³⁺（90（?））的离子半径大,所以Bi³⁺的掺入会导致石榴石膜晶格膨胀,进而造成与钆镓石榴石（GGG）衬底之间的晶格失配;为了补偿掺Bi³⁺引起的晶格膨胀,实验中选择比Y³⁺（90（?））离子半径小的Tm³⁺（86.9（?））共同掺杂;同时利用Ga³⁺取代YIG中四面体的24d位上的Fe³⁺,可以有效降低石榴石膜的饱和磁化强度,进而在一定程度上降低薄膜的饱和外场。本文设计并采用LPE方法制备了不同生长温度和厚度的单晶（TmBi）₃（FeGa）₅O₁₂膜,并基于对石榴石薄膜磁各向异性理论的分析,研究了晶格失配、生长温度和应力等因素对（TmBi）₃（FeGa）₅O₁₂薄膜易磁化轴取向及磁各向异性的影响。首先对单晶（TmBi）₃（FeGa）₅O₁₂石榴石膜的磁滞回线、晶格失配和膜中Bi³⁺含量等进行了测试表征及计算分析。研究发现:所制备的石榴石膜始终表现为面外各向异性;外延膜厚度大于1μm时,形状各向异性对磁各向异性产生的影响可以忽略;相较于生长感生各向异性,磁各向异性的变化中主要是由应力各向异性占主导。其次对（TmBi）₃（FeGa）₅O₁₂膜进行法拉第测试,由测试结果计算出该石榴石膜的Verdet常数为11.8×10⁴rad/Tm@1064nm,是常用磁光材料TGG的3000倍;表明（TmBi）₃（FeGa）₅O₁₂单晶膜在磁光器件中具有很大的发展潜力。综合薄膜的磁光性能和薄膜质量等分析,得出生长温度为893℃是最佳生长温度,并在此温度下制备了磁光开关中的法拉第转子。当测试波长为1310 nm时,其比法拉第旋角为0.068°/μm,外加饱和磁场为70 G_S,（TmBi）₃（FeGa）₅O₁₂单晶膜具有较大的比法拉第旋角和较小的外加磁场,能够满足设计要求。最后设计、仿真并加工了工作在1310nm的磁光开关。更多还原

【Abstract】 Liquid phase epitaxy（LPE）has so far been one of the best techniques for the preparation of single crystal garnet films.A lot of research shows that Bi³⁺can replace Y³⁺ions in yttrium iron garnet（YIG）to grow Bi-substituted garnet（Bi:YIG）films.Bi:YIG film has larger specific Faraday rotation angle than that of pure YIG,and its easy magnetization axis can easily tuned to out of plane orientation,which allows to operate under small external magnetic field.Thus Bi:YIG film meet the demand of miniaturization and energy saving of magneto-optical devices.Because the ionic radius of Bi³⁺（108（?））is larger than that of Y³⁺（90（?））,the doping of Bi³⁺will lead to lattice expansion of the garnet film,resulting in lattice misfit with the gadolinium gallium garnet（GGG）substrate.In order to neutralize the lattice expansion caused by Bi³⁺,Tm³⁺（86.9（?））with smaller ionic radius than Y³⁺（90（?））is selected to co-doping.Meanwhile,Ga³⁺is doped to replace Fe³⁺at 24d site of tetrahedron in YIG to reduce the saturation magnetization intensity of the garnet film and thus the saturation field of the film can be reduced to a certain extent.In this paper,the single crystal（TmBi）₃（FeGa）₅O₁₂ films with different growth temperatures and thicknesses are designed and prepared by LPE method.Based on the analysis of the magnetoanisotropy theory of garnet films,the effects of lattice misfit,growth temperature and stress on the magnetoanisotropy of（TmBi）₃（FeGa）₅O₁₂ films are investigated.Firstly,the hysteresis loop,lattice mismatch and Bi³⁺content of（TmBi）₃（FeGa）₅O₁₂garnet films are measured and characterized.The results show that the garnet films always exhibited out-of-plane anisotropy;when the thickness of the epitaxial film is more than 1μm,the influence of shape anisotropy on the magnetoanisotropy can be ignored.Stress-induced anisotropy dominated the variation of magnetic anisotropy compared to growth-induced anisotropy.Secondly,Faraday test is carried out on（TmBi）₃（FeGa）₅O₁₂ film and the Verdet constant of the garnet film is calculated as 11.8×10⁴rad/Tm@1064nm.It is 3000 times higher than that of TGG,which shows that（TmBi）₃（FeGa）₅O₁₂ single crystal films have great potential for development in magneto-optical devices.Based on the analysis of magneto-optical properties and film quality,it is concluded that a growth temperature of 893℃ is the optimum growth temperature,and a Faraday rotor in a magneto-optical switch was fabricated.When the test wavelength is 1310 nm,the specific Faraday rotation angle is 0.068°/μm,and the external saturation magnetic field is 70 G_S.The（TmBi）₃（FeGa）₅O₁₂ single crystal film has a larger than specific Faraday rotation angle and a smaller external magnetic field,which can meet the design requirements.Finally,the magneto-optical switch working at 1310nm is designed,simulated and processed.更多还原