文章基本信息

标题：Crossover from a heavy fermion to intermediate valence state in noncentrosymmetric Yb₂Ni₁₂(P,As)₇
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作者：W. B. Jiang ; L. Yang ; C. Y. Guo 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
DOI：10.1038/srep17608
出版社：Springer Nature
摘要：We report measurements of the physical properties and electronic structure of the hexagonal compounds Yb₂Ni₁₂ Pn ₇ ( Pn = P, As) by measuring the electrical resistivity, magnetization, specific heat and partial fluorescence yield x-ray absorption spectroscopy (PFY-XAS). These demonstrate a crossover upon reducing the unit cell volume, from an intermediate valence state in Yb₂Ni₁₂As₇ to a heavy-fermion paramagnetic state in Yb₂Ni₁₂P₇, where the Yb is nearly trivalent. Application of pressure to Yb₂Ni₁₂P₇ suppresses T _FL, the temperature below which Fermi liquid behavior is recovered, suggesting the presence of a quantum critical point (QCP) under pressure. However, while there is little change in the Yb valence of Yb₂Ni₁₂P₇ up to 30 GPa, there is a strong increase for Yb₂Ni₁₂As₇ under pressure, before a near constant value is reached. These results indicate that any magnetic QCP in this system is well separated from strong valence fluctuations. The pressure dependence of the valence and lattice parameters of Yb₂Ni₁₂As₇ are compared and at 1 GPa, there is an anomaly in the unit cell volume as well as a change in the slope of the Yb valence, indicating a correlation between structural and electronic changes.