Charge fluctuation in Sm 3Te 4

Abstract

Ultrasonic measurements for a valence-fluctuation compound Sm 3Te 4 have been performed. Considerable dispersion around 120 K due to a thermal hopping motion of 4f-electron among Sm 2+ and Sm 3+ has been observed in the ultrasonic attenuation. The relaxation time of the charge fluctuation 2π τ becomes infinite at low temperatures following as τ= τ 0exp( E/ k B T), here 2 πτ 0=2.5×10 −13 s and E=0.136 eV. The ln T dependence of the elastic constants similar to a two-level system of amorphous glass compounds is observed at low temperatures below 15 K. These results indicate a two-level system of the 4f-electron tunneling in the random potential of Sm 2+ and Sm 3+ ions due to the charge glass state.