EXAFS investigation of the local structure in URu2−xFexSi2 : Evidence for distortions below 100 K
EXAFS investigation of the local structure in URu2−xFexSi2 : Evidence for distortions below 100 K
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EXAFS 对 URu2–xFexSi2 局部结构的研究：100 K 以下扭曲的证据
DOI：
10.1103/physrevb.102.014109
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发表时间：
2020
影响因子：
3.7
通讯作者：
Maple, M. B.
中科院分区：
文献类型：
--
作者：
Bridges, F.;Dudschus, R.;Mackeen, C.;Keiber, T.;Booth, C. H.;Maple, M. B.
X射线吸收测量在U，Ru，和Feedges报告的隐藏顺序（HO）材料（，0.05，0.08，0.10，0.12，0.15，和0.20）作为的函数和温度。当Fe取代Ru时，Fe附近的局域结构略有收缩，第一近邻Fe-Si键长减小。更重要的是，在Debye-Waller因子（对分布函数的宽度）图中，在80 - 100 K（相干温度）以下观察到过量无序;在低温度下，数据偏离通常的爱因斯坦或相关德拜模型图。这种无序在Ru-Si键中最为显著，在80 K以下会增加。这些结果表明，在80 - 100 K以下出现了具有类对称性的局部正交畸变。一个模型，描述了这些地方的扭曲，并讨论了在其他测量，表明在低的四重对称性的破坏。此外，在100 K以下的温度范围内，Ru-Si对和德拜拟合之间的差的平方根可以作为这种正交畸变的序参量。这个量是一个长度相关的，在正交相和晶格常数之间的差异，并提供了这种扭曲和之间的联系。X射线吸收近边结构（XANES）的测量也表明，有没有变化的边缘位置下降到0.1 eV的任何边缘作为一个函数，在HO制度。
X-ray absorption measurements at the U, Ru, and Feedges are reported for the hidden order (HO) material(, 0.05, 0.08, 0.10, 0.12, 0.15, and 0.20) as a function ofand temperature. When Fe is substituted for Ru, the local structure about Fe shrinks slightly and the first neighbor Fe-Si bond length decreases by. More importantly excess disorder is observed below 80–100 K (the coherence temperature) in plots of the Debye-Waller factor(is the width of the pair distribution function); at lowthe data deviate from the usual Einstein or correlated-Debye model plots. This excess disorder is most prominent for the Ru-Si bond, andactually increases below 80 K. These results suggest a local orthorhombic distortion with-like symmetry that develops below 80–100 K. A model that describes these local distortions is presented, and discussed in terms of other measurements that indicate a breaking of fourfold symmetry at low. In addition, the square root of the difference betweenfor the Ru-Si pair and a Debye fit to these data serves as an order parameter for this orthorhombic distortion, in the temperature range below 100 K. This quantity is a length related to, the difference between theandlattice constants in the orthorhombic phase, and provides a connection between this distortion and. X-ray absorption near edge structure (XANES) measurements also show that there are no changes in the edge positions down to 0.1 eV for any edge as a function of, forin the HO regime.