Search

Abstract: We have carried out soft and hard X-ray spectroscopy of Sm-based filled skutterudites SmFe4 P12 and SmOs4 Sb12. Sm 3d–4f resonant photoemission and Sm 3d–4f X-ray absorption spectra suggest that SmOs4 Sb12 has much more strongly mixed Sm valence state than SmFe4 P12 in the bulk. On the other hand, the Sm trivalent state is dominant on the surface of SmOs4 Sb12. [Copyright &y& Elsevier]

Sm-based heavy-fermion compound SmOs4Sb12 has been investigated by soft x-ray (hnu=1070-1600 eV) and hard x-ray (HX; hnu=7932 eV) spectroscopy. The HX photoemission spectroscopy clearly demonstrates that the strongly mixed-valence state and the heavy-fermion state coexist in the bulk. It is found that the Sm valence decreases below 100 K, indicating that the Kondo coherence develops with approaching the proposed Kondo temperature. Our theoretical analyses suggest that the origin of the coexistence in SmOs4Sb12 is the coincidence of two conditions, namely, (i) the energy difference between Sm divalent and trivalent states is very small and (ii) the hybridization between Sm 4f and conduction electrons is weak.