Intermediate-Valence Behavior of YbCu_<5-x>Al_x around Quantum Critical Point Measured by Resonant Inelastic X-ray Scattering at Yb L_3 Absorption Edge(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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An x-ray spectroscopy study was performed for YbCu_<5-x>Al_x (x = 0.0-2.0) using high-resolution partial-fluorescence yield (PFY) and resonant inelastic x-ray scattering (RIXS) at the Yb L_3 absorption edge. From a careful analysis of the PFY and RIXS spectra, the mean-valence of Yb was estimated and is found to increase quite rapidly for compositions between 0≤x≤1.0, indicating strong intermediate-valence behavior. The mean valence continues to increase gradually with x and becomes nearly trivalent for x = 2.0. Our results, however, reveal that valence fluctuation occurs even at x = 1.5, for which non-Fermi liquid quantum critical behavior is known. The valence evolution cannot be explained solely in terms of chemical pressure effects. The study suggests the role of valence-coupled spin fluctuations for the quantum critical behavior.
社団法人日本物理学会の論文
2007-12-15