Site-specific valence fluctuations in Eu 3 Pd 20 Ge 6 studied via Mössbauer and x-ray absorption spectroscopies

Some Ce, Eu, Sm, and Yb compounds are known to be valence-fluctuating compounds. 1 In these compounds, the ground state in one of the valence states is magnetic and that in the other is nonmagnetic. Therefore, magneticsusceptibility measurement provides a rough estimation of the average valence. In addition, the ionic radius depends on the valence state even in the same element. Therefore, another estimation of the average valence is given by the degree of deviation from the lanthanide contraction of the lattice constant in a series of rare-earth compounds. Since rareearth atoms in most valence-fluctuation systems investigated previously occupy one site, 2–19 the analysis of the magnetic susceptibility and the investigation of the lattice constant are useful in estimating their valence states at rare-earth sites. These approaches apply to the investigation of the physical properties of the valence-fluctuating compound SmB 6 , for example. 2–6 However, these estimations fail in a compound with multiple sites for rare-earth atoms. It is also difficult to estimate the fluctuation time for each site.