以X光吸收光譜探討CePt2+x之電子結構

Electronic structure of CePt2+x studied by x-ray absorption spectroscopy

向得龍(Te-Lung Hsiang)

指導教授 ： 張經霖

淡江大學/理學院/物理學系碩士班/碩士(2007年)

https://doi.org/10.6846/TKU.2007.00006

摘要

本篇論文利用X光吸收近邊緣結構 (X-ray absorption near edge structure) 對CePt2+x塊材系列樣品進行研究，此塊材系列樣品有x = 0、0.5和1共三種，其中對於鈰元素 (Cerium) 我們量測了其L3-edge和M4,5-edge的螢光訊號；對於鉑元素 (Platinum) 我們完成了L3-edge螢光訊號的測量。在Ce L3-edge發現CePt2+x塊材系列樣品其L3-edge譜圖具有Ce3+與Ce4+特徵組態結構，其中位於5726 eV的主峰A乃反映Ce3+ (4f 15d) 特徵而另一位於5733 eV則是由Ce4+ (4f 05d)所貢獻。而Ce的L3-edge和M4,5-edge譜圖形狀暗示著有Ce4+存在且Ce離子的價數仍較接近+3價。 Ce的價數計算可透過trivalent feature A 和 tetravalent feature B的相對強度作譜圖擬合計算。我們的研究暗示磁性熵會隨Pt的增加而減少，此與樣品的比熱量測結果一致。

關鍵字

稀土合金 ； 近邊吸收結構

並列摘要

This study presented the results of x-ray absorption near edge structure ( XANES ) study of a series of CePt2+x samples, where x = 0. 0.5 and 1. We had measured L3-edge and M4,5-edge for Ce element and L3-edge for Pt element in fluorescence mode. We have find that the L3 XANES of Ce of our samples are all consist with a main 3+ peak and a small 4+ feature. Peak A located at around 5726 eV directly reflects the Ce3+ (4f 15d) contribution. The small feature B located at about 5733 eV is contributed by the Ce4+ (4f 05d) state. The spectral shapes indicate that the Ce valence states are mainly 3+ with small amount of 4+ states. The average Ce valence can be estimated by the relative intensities of the trivalent feature A and the tetravalent feature B. Our results indicate that the magnetic entropy decreases with Pt concentration, which is consistent with the heat capacity measurements.

並列關鍵字

XANES ； Cerium

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