近年來自旋頓挫態系統是一個熱門的研究主題，此系統的材料有著奇特的自旋排列使得樣品在外加磁場及壓力下與一般磁性材料有著不一樣的特性。常見的自旋頓挫態晶格結構有三角晶格、籠紋晶格、尖晶石結構及焦綠石晶格。
　　本篇所討論的樣品Cu3Bi(SeO3)2O2Cl屬於第二類多鐵材料且結構為籠紋晶格，是一個有趣的自旋頓挫態材料。此樣品除了具有多鐵性外，同時也具有各向異性的磁性行為，引起我們研究的興趣。實驗透過化學摻雜膨脹及物理壓縮的方式改變Cu3Bi(SeO3)2O2Cl的結構來了解其結構改變對於自旋排列的影響。
　　化學摻雜部分利用Te及Br分別來取代Se及Cl讓樣品單位晶格體積增大，而且在不同的參考文獻中Te會讓Cu3Bi(SeO3)2O2Cl的space group從Pmmn變為Pcmn; Br則是維持不變。Cu3Bi(Se1-xTexO3)2O2Cl (0≤x≤1.0) 系列的XRD數據經過精細結構分析軟體GSAS的分析後，發現摻雜濃度大於60%後樣品space group會從Pmmn轉變為Pcmn，且得出其晶格常數a及b會隨著Te原子摻雜的濃度增加而變大，c則是變小。整體單位晶格體積是增加的，所以Te摻雜屬於非等向性的膨脹;而Cu3Bi(SeO3)2O2Cl1-xBrx (0≤x≤1.0)系列則是a、b及c都增大，屬於等向性膨脹。
　　磁性方面的量測，Te摻雜樣品的反鐵磁相變溫度TN及自旋翻轉磁場Hc隨著Te摻雜濃度增加會跟著增加，但是飽和磁化強度Ms則會減少;而Br摻雜樣品則是飽和磁化強度Ms隨著Br摻雜濃度增加而些微增加，反鐵磁相變溫度TN及自旋翻轉磁場Hc並沒有大太的改變。物理壓縮方面的磁性量測則是隨著壓力的增加，Cu3Bi(SeO3)2O2Cl的反鐵磁相變溫度TN及飽和磁化強度Ms增加，但是自旋翻轉磁場Hc減少。
　　從物理/化學壓力效應的數據圖表中可以得知非等向性膨脹對於Cu3Bi(SeO3)2O2Cl樣品的磁性有著明顯的影響。這些非等向性壓力效應的實驗結果可以由模擬亞鐵磁性層間的作用來解釋，而經由非等向性壓力效應來控制自旋翻轉轉變有助於了解Cu3Bi(SeO3)2O2Cl磁場誘發變磁的機制。

In recent years, the frustrated spin system has been a popular research topic. In these systems, the magnetic ions have confined to peculiar lattice geometries that exhibits the exotic physical properties under external magnetic field and pressure, which are very much different from the general magnetic materials. The common frustrated-spin lattices have triangular lattice, Kagome lattice, spinel structure and pyrochlore lattice.
　　The Cu3Bi(SeO3)2O2Cl, belongs to type II multiferroic material, the spin 1/2 Cu2+ ions form the pseudo-Kagome lattice, is an interesting spin-frustrated material. Apart from multiferroic behavior, it also exhibits anisotropic magnetic property. These unique magnetic and multiferroic properties motivated us to further understanding of these materials under the chemical/physical pressure conditions. Unit cell expansion studies were carried out with chemical doping of Te and Br ions at Se and Cl sites respectively. The physical pressure used for the compression studies.
　　The XRD (X-ray diffraction) data of the Cu3Bi(Se1-xTexO3)2O2Cl (0 ≤ x ≤ 1.0) series were analyzed by rietveld refinement analysis by using the software GSAS. For doping concentration x  0.6, the crystal structure changes from Pmmn to Pcmn space group. The lattice constants a and b increase, but c decreases with increasing concentration of Te doping, which indicates Te doping anisotropically expand the unit cell. However, for the case Cu3Bi (SeO3) 2O2Cl1-xBrx (0 ≤ x ≤ 1.0), the lattice constants a, b and c increases with x that signifies the isotropic expansion of unit cell.
　　The effects of pressure on the magnetic properties have been studied in Kagome Cu3Bi(Se1-xTexO3)2O2Cl (0 ≤ x ≤ 1.0) and Cu3Bi(SeO3)2O2Cl1-xBrx (0 ≤ x ≤ 1.0) polycrystalline samples. For anisotropic expansion, the antiferromagnetic transition temperature (TN) and the critical field (Hc) of metamagnetic spin-flip transition increase with Te doping. However, the value of saturation magnetization (Ms) decreases with Te doping concentration. For isotropic expansion, Ms TN and Hc shows only minute change under Br doping. The compression of unit cell by external pressure shows the TN and Ms increase, while the Hc reduces.
　　Our comprehensive studies of physical/chemical pressure indicate the anisotropic expansion shows prominent influence on the magnetic properties of Cu3Bi(SeO3)2O2Cl. This can be explained by the modulation of competition between ferrimagnetic intralayers interactions. The route to control the spin-flip transition by anisotropic pressure effects might be helpful to understand the mechanism of field-induced metamagnetic Cu3Bi(SeO3)2O2Cl.

致謝 i
論文摘要 iii
Abstract v
目錄 viii
圖目錄 x
第一章 簡介 1
1-1 多鐵性介紹 1
1-2 自旋頓挫態系統介紹 6
1-3 Cu3Bi(SeO3)2O2Cl 9
1-4 研究動機 14
第二章 實驗儀器介紹 15
2-1 X-Ray粉末繞射儀 15
2-2 拉曼光譜儀 17
2-3 磁性量測儀器 20
2-3-1 超導量子干涉磁量儀 20
2-2-2 磁性量測方法 25
2-4 高壓實驗 28
第三章 實驗結果與討論 30
3-1 固態合成法製備樣品 30
3-2 X-ray繞射分析 33
3-2-1 Cu3Bi(Se1-xTexO3)2O2Cl的XRD分析 33
3-2-2 Cu3Bi(SeO3)2O2Cl1-xBrx的XRD分析 47
3-3 拉曼光譜分析 52
3-4 磁性量測 53
3-4-1 Cu3Bi(Se1-xTexO3)2O2Cl的磁性量測結果與討論 53
3-4-2 Cu3Bi(SeO3)2O2Cl1-xBrx的磁性量測結果與討論 58
3-5 Cu3Bi(SeO3)2O2Cl在壓力下的磁性量測結果與討論 61
第四章 結論 65
參考文獻 67

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