Valence fluctuation of Sm3Se4

Abstract
The fluctuating valence state of Sm3Se4 has been investigated by measurements of ultrasonic dispersion and AC conductivity. A pronounced frequency dependence of the elastic constants and ultrasonic attenuation near 120K is observed, which is caused by the thermally activated hopping of 4f electrons. The AC resistivity also shows marked frequency and temperature dependences, which are governed by the 4f hopping conduction and the thermally assisted quantum mechanical tunnelling among the localised states in the randomly distributed potentials. The 4f hopping rate determined by the present experiments has the activation-type temperature dependence, tau = tau 0 exp(E0/kT), where tau 0=2.4*10-13 s and the activation energy is E0=0.14 eV.

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