La2-xSrxNiO4的電荷條制之X-ray散射研究

Study of the charge stripes in La2-xSrxNiO4 using X-ray scattering

簡名紀(Ming-Ji Jian)

指導教授 ： 杜昭宏

淡江大學/理學院/物理學系碩士班/碩士(2011年)

https://doi.org/10.6846/TKU.2011.00686

摘要

La2-xSrxNiO4 (LSNO)是藉由La2NiO4摻雜金屬元素鍶(Sr)所形成的。隨著溫度及摻雜量的變化，LSNO會形成電荷有序排列(charge-ordering)和自旋有序排列(spin-ordering)兩種不同的電子結構排列狀態。此論文是利用X-ray 散射，來研究La2-xSrxNiO4系統中由電荷有序排列所形成的調制結構與Sr含量的關係，也可藉此來探討La2-xSrxNiO4系統由調制結構所產生的相變化。因調製結構的波向量Q與Sr含量有密切相關，所以在摻雜量x=0.33中，電荷與電子自旋調制結構的Q值在某些位置是重疊的。與其它摻雜量相比，其繞射峰的積分強度與半高寬之結果明顯不同，而量測方式的不同，也會導致隨溫度變化的行為曲線有所不同。藉由不同摻雜量間的互相比較，我們觀察到電荷條紋有序排列結構確實會因摻雜量的不同，而導致在降溫過程中產生不同的變化行為。

關鍵字

La2-xSrxNiO4 ； 電荷條紋

並列摘要

La2-xSrxNiO4 (LSNO) is isostructural to the high-Tc superconductor La2-xSrxCuO4 (LSCO), but remains no appearance of superconductivity even up to about 75% contents of Sr. This has been known to be caused by the formation of static charge and spin modulations. As x-rays are sensitive to charges, we report the study of the charge modulation in LSNO as a function of temperature and the concentration of Sr using high resolution x-ray scattering. The transition temperature and wavvector for the formation of charge modulation were observed to be dominated by the concentrations of Sr. In addition, for the optimal doped compound, x~0.33, the evolution of the correlation length as a function of temperature along the L-direction displays an unusual behavior around the transition temperature, suggesting the possible existence of inverse melting.

並列關鍵字

La2-xSrxNiO4 ； Charge stripe

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