摻雜釤元素的釔鐵石榴石之磁性探討
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2020
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本論文探討由脈衝雷射蒸鍍法在c平面藍寶石基板上所製備知釔釤鐵石榴石薄膜的晶體結構，表面形貌及磁光特性。薄膜的厚度為100 nm，製備條件為氧壓 3×〖10〗^(-7) mbar，基板溫度為525 ℃，雷射在靶材上的單位面積能量3.5 J/cm2，並在大氣下用高溫爐以1050 ℃進行4小時的熱退火。
X光繞射光譜得知大部分薄膜為多晶結構，而在取代量為x = 2.0和2.5時則是非晶結構。拉曼散射光譜證實所有薄膜維持YIG的立方對稱性。分析取得的晶格常數在12.3046～12.4669 Å之間，僅x = 1.5的薄膜其晶格常數小於塊材的YIG數值。
薄膜的表面形貌以圓形為主，部分取代的薄膜樣品表面的顆粒較小也較一致，粗糙度也較小。所有薄膜樣品的方均根粗糙度在6.84～23.08 nm之間，和取代量無明顯關係。
薄膜樣品在340～560 nm的波長範為可以觀察到磁滯曲線，代表薄膜具有磁的垂直異向性。其矯頑場在5～280 mT之間，飽和法拉第旋轉角在1.9×〖10〗^(-2)～0.747 mrad之間。兩者和取代量的關係是到取代量從x=0.0開始變大，x = 1.5～2.0達到最大後，到x = 3.0之間變小。
In this thesis, we report the crystal structure, surface morphology, and magneto-optical properties of Sm doped yttrium iron garnet thin films grown by pulsed laser deposition on c-sapphire substrates. The deposition are carried out in the oxygen pressure at 3×〖10〗^(-1) mbar, substrate temperature at 525 ℃, and at the laser energy density of 3.5 J/cm2. After deposition, thin films are annealed at 1050 ℃ for 4 hours in atmosphere. X-ray diffraction (XRD) spectroscopy shows that the films are of polycrystalline structure with the exception of x = 2.0 and 2.5, where they are amorphous structure. Raman scattering spectroscopy confirms that all films maintain the cubic symmetry of yttrium iron garnet (YIG). The lattice constant of the thin films obtained from XRD are between 12.3046 and 12.4669 Å. Only the film with x = 1.5 has a lattice constant smaller than the bulk value of YIG. The surface morphology of the films is mainly in circular shape. The particle size on the surface of the partially substituted thin film samples is smaller and more consistent, and the roughness is also smaller. The root-mean-square roughness of all thin film samples is between 6.84 nm and 23.08 nm, which has no obvious dependence of the amount of substitution. Hysteresis loops are observed with magneto-optical Faraday effect in the wavelengths between 340 and 560 nm, which represents that the thin films have magnetic perpendicular anisotropy. The coercive fields are between 5 and 280 mT, and the saturation Faraday rotation angles are between 0.019 and 0.747 mrad. Both the coercive field and saturation Faraday rotation angle increase with Sm content until it reaches x = 1.5, and then decreases after x = 2.0.
In this thesis, we report the crystal structure, surface morphology, and magneto-optical properties of Sm doped yttrium iron garnet thin films grown by pulsed laser deposition on c-sapphire substrates. The deposition are carried out in the oxygen pressure at 3×〖10〗^(-1) mbar, substrate temperature at 525 ℃, and at the laser energy density of 3.5 J/cm2. After deposition, thin films are annealed at 1050 ℃ for 4 hours in atmosphere. X-ray diffraction (XRD) spectroscopy shows that the films are of polycrystalline structure with the exception of x = 2.0 and 2.5, where they are amorphous structure. Raman scattering spectroscopy confirms that all films maintain the cubic symmetry of yttrium iron garnet (YIG). The lattice constant of the thin films obtained from XRD are between 12.3046 and 12.4669 Å. Only the film with x = 1.5 has a lattice constant smaller than the bulk value of YIG. The surface morphology of the films is mainly in circular shape. The particle size on the surface of the partially substituted thin film samples is smaller and more consistent, and the roughness is also smaller. The root-mean-square roughness of all thin film samples is between 6.84 nm and 23.08 nm, which has no obvious dependence of the amount of substitution. Hysteresis loops are observed with magneto-optical Faraday effect in the wavelengths between 340 and 560 nm, which represents that the thin films have magnetic perpendicular anisotropy. The coercive fields are between 5 and 280 mT, and the saturation Faraday rotation angles are between 0.019 and 0.747 mrad. Both the coercive field and saturation Faraday rotation angle increase with Sm content until it reaches x = 1.5, and then decreases after x = 2.0.
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釔鐵石榴石, 釤, 脈衝雷射蒸鍍法, 法拉第磁光效應, yttrium iron garnet, Samarium, pulsed laser deposition, magneto-optic Faraday effect