Preparation and orientation mechanism analysis of (BiTm)&lt;sub&gt;3&lt;/sub&gt;(GaFe)&lt;sub&gt;5&lt;/sub&gt;O&lt;sub&gt;12&lt;/sub&gt; magneto-optical single crystal film with out-of-plane orientation

Xue Yang,Jian-Tao Huang,Fei-Ming Bai,Ding Zhang,Qi-Ye Wen,Zhi-Yong Zhong,Qing-Hui Yang,Huai-Wu Zhang

doi:10.7498/aps.70.20202209

Abstract

Liquid-phase epitaxy (LPE) is one of the best techniques for the preparation of single crystal garnet films. However, the specific Faraday rotation angle of Yttrium iron garnet (YIG) is small, and its easy magnetization axis is parallel to the film surface. The YIG requires a large external saturation field, which cannot meet the development needs of magneto-optical devices. It is found that Bi-substituted YIG(Bi:YIG) film has a larger specific Faraday angle. By adjusting the easy magnetization axis of Bi: YIG perpendicular to the film surface, the saturation magnetization of Bi: YIG can be reduced, so that it can work under a small external magnetic field. This meets the development needs of miniaturization and energy saving of magneto-optical device. The saturation magnetization of garnet film can be effectively reduced by substituting Ga3+ for YIG crystal, mainly for Fe3+ at the 24d position of its tetrahedron. And the lattice constants of Gd3Ga5O12 (GGG) and YIG are 1.2383 nm and 1.2376 nm, respectively. However, the radius of Bi3+ (10.8 nm) is larger than that of Y3+ (9.0 nm), the lattice mismatch of garnet film increases with the incorporation of Bi3+. In order to neutralize the lattice expansion caused by Bi3+, Tm3+ (8.69 nm) with a radius smaller than that of Y3+ (9.0 nm) is selected. Based on the theoretical analysis of the magnetocrystalline anisotropy of garnet film, (BiTm)3(GaFe)5O12 mono-crystalline films with different growth temperatures and different thickness values are grown by LPE on GGG (111) substrates. The experimental results show that when the thickness of epitaxial film is greater than 1 μm, the influence of shape anisotropy on magnetocrystalline anisotropy can be ignored. With the increase of growth temperature, the substitution number of Bi3+ ions decreases gradually, the lattice constant of epitaxial film decreases gradually, and the lattice mismatch first decreases and then increases. Then, the state of compressive stress gradually changes into that of tensile stress. Compared with growth-induced anisotropy, the stress-induced anisotropy is dominant in the change of magnetocrystalline anisotropy. The Verdet constant of (BiTm)3(GaFe)5O12 film is 11.8 × 104 rad/Tm@1064 nm. The results show that the prepared (BiTm)3(GaFe)5O12 mono-crystalline films have great development potential in magneto-optical devices.

Highlights

The results show that the prepared (BiTm)3 (GaFe)5O12 mono-crystalline films have great development potential in magneto-optical devices
易磁化轴为面外的 (BiTm)3(GaFe)5O12 膜在入射波长为 1064 nm 时, 其 Verdet 常数为 11.8 × 104 rad/Tm, 面外饱和场小于 200 Oe, 其磁光性能优异

Summary

Introduction

本文基于对石榴石薄膜磁各向异性的理论分析, 采用液相外延 (liquid-phase epitaxy, LPE) 法在钆镓石榴石 (gadolinium gallium garnet, GGG) 基底上制备了单晶 (BiTm)3(GaFe)5O12 膜, 并研究了其磁各向异性性能. (BiTm)3(GaFe)5O12 膜的 Verdet 常数为 11.8 × 104 rad/Tm@1064 nm, 是常用磁光材料 TGG 的 3000 倍; 其外加工作磁场小于 200 Oe, 有利于实现磁光器件的小型化和薄膜化. 采用 LPE 工艺以 GGG 为衬底在不同的生长温度下制备了一系列不同厚度的 (BiTm)3(GaFe)5O12 膜, 详细研究了其磁各向异性性能, 并对应力各向异性、生长感生各向异性、形状各向异性和立方磁晶各向异性对其性能的影响进行了理论和实验分析. (1) 式中 Htotal 表示磁各向异性等效场, K1(x, y) 表示一阶立方磁晶各向异性常数, Kug 表示生长各向异性常数, Kuλ 表示应力各向异性常数, Kshape 表示 GGG(111) 的晶格常数为 12.383 Å, YIG 的晶格常数为 12.376 Å, 然而 Bi3+(108 Å) 的半径比 Y3+(90 Å) 的半径大, 107801-2

Results

Conclusion