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    題名: 利用X光吸收光譜研究La53Sr1/3NiO4電子結構
    其他題名: Electronic structure of the La5/3Sr1/3NiO4 studied by X-ray Absorption Spectroscopy
    作者: 梁又仁;Liang, Yow-Ren
    貢獻者: 淡江大學物理學系碩士班
    彭維鋒;Pong, Way-Faung
    關鍵詞: X光吸收近邊緣結構;延伸X光吸收精細結構;電荷密度波;XANES;EXAFS;CDW
    日期: 2011
    上傳時間: 2011-12-28 18:05:57 (UTC+8)
    摘要: 本論文主要以X光吸收光譜實驗研究單晶樣品La5/3Sr1/3NiO4的電子與原子結構。實驗包含室溫時不同極化方向O K- edge、Ni K-edge、La L3-edge與La M5-edge X光吸收近邊緣結構(X-ray absorption near edge structure,XANES),以及分別在不同溫度下量測O K- edge、La L3-edge、La M5-edge和Ni K-edge延伸X光吸收精細結構(Extended x-ray absorption fine structure,EXAFS)。由不同極化方向O K-edge與Ni K-edge XANES光譜圖中發現樣品有著結構異向性,並且從La L3-edge與La M5-edge XANES光譜圖可印證樣品絕緣層的存在與影響電子的傳輸方向。由不同溫度的O K-edge XANES光譜顯示,在溫度T = 240K時電荷條紋與溫度T = 180K電子自旋條紋形成時由於未佔據態數目改變造成電阻非線性的變化。並且從Ni K-edge EXAFS光譜圖指出,隨著溫度改變,Ni原子周圍的原子結構是相似的,這顯示樣品中CDW的轉變機制與原子結構變化並無明顯直接關聯。
    The electronic and atomic structures of the single crystal La5/3Sr1/3NiO4 were investigated by angle-dependent x-ray absorption near-edge structure (XANES) at O and Ni K-, La L3-, and La M5-edges at various temperatures. Apart from this, the extended x-ray absorption fine structure (EXAFS) at Ni K-edge was measured at different temperatures. These studies show the structural and electronic anisotropic nature of La5/3Sr1/3NiO4. From the spectra of different polarization of the La L3-edge and La M5-edge XANES, it is evident that this spacer layer (La-O) affect the electronic structure. According to the O K-edge spectra at different temperatures, when the charge stripes at T = 240K and spin stripesthe at T = 180K was formed, the unchanged number of unoccupied states can caused the non-linear changes of resistance. The spectra of the Ni K-edge EXAFS indicates that the atomic structure around the Ni atom does not change as the temperature is varied. Thus we find that the charge density wave phase and the dynamical properties of La5/3Sr1/3NiO4 have no direct relation to the atomic structure.
    顯示於類別:[物理學系暨研究所] 學位論文

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