- 學位論文
利用X光吸收光譜研究單晶結構的Ni3TeO6
X-ray absorption studies of Ni3TeO6 single crystal
摘要
本論文主要以同步輻射實驗研究單晶結構Ni3TeO6的電子、原子結構關聯性。實驗包含在不同溫度下X光吸收光譜之吸收近邊緣結構(XANES)、延伸X光吸收精細結構(EXAFS)、X光磁圓偏振二向性(XMCD)、X光線偏振二向性(XLD)。Ni3TeO6隨著溫度從低溫升至室溫，量測沿著樣品不同的方向，意即ab-平面和c軸的磁化率，分別出現不同的特徵峰。由XANES的實驗發現隨著溫度從低溫升至室溫，Ni皆為二價存在。在EXAFS的變溫度實驗中，即使在磁結構相變後，Ni-O鍵長沒有明顯的改變。從XLD實驗結果中發現，由低溫回溫至室溫，其中在磁相變溫度後，電子軌域由3d3z2-r2轉向 3dx2-y2軌域。最後沿c軸量測XMCD變溫實驗，溫度在TSO ≈ 59K，發現鐵磁性的XMCD譜圖。上述的實驗結果，是因為Ni自旋有序才能產生一連串的物理現象。
並列摘要
Here we report the temperature dependence of anisotropic electronic and magnetic structures of Ni3TeO6 single crystalline samples by means of dichroic XAS techniques. Magnetic measurements have revealed an existence of weak Ni-Ni FM interaction near ~ 60 K (TSO) with different peak pointing along the crystallographic c-axis. Below Neel Temperature, TN ~ 52 K, the sample stabilizes in AFM state with the spin axis also parallel to the c-axis. The Ni L3,2-edge XLD plots have revealed contributions both from magnetic interactions (below the spin ordered phase, T ≤ TSO) and temperature independent crystal field effects above TSO. The XLD results show that above TSO, the Ni 3d eg electrons will remain in in-plane 3dx2-y2 orbitals and switches to the out-of-plane 3d3z2-r2 orbitals below TSO. Ni L3,2-edge with H // c along the crystallographic c-axis existence of XMCD spectra. Due to Ni3TeO6 Ni-spin existence, which produce a series of physical phenomena.