Temperature dependence of Sm valence in SmB₆studied by X-ray absorption spectroscopy

Abstract

X-ray absorption spectra of a valence-fluctuated Kondo insulator SmB6 have been studied near the Sm L3-edge at temperatures below 300 K. The average valence of Sm ions in SmB6 was deduced as 2.59 at 300 K; it shows a characteristic temperature behaviour with three anomalies at T = 15, 50 and 150 K. These temperatures correspond to the characteristic energies of SmB6 in macroscopic measurements. The present results imply that the Sm-4f electrons strongly hybridize with the conduction electrons and play an important role in the gap formation.