Elastic Anomalies of Single Crystalline Rh₁₇S₁₅ Associated with Structural Fluctuation

Abstract

We have studied elastic properties by ultrasonic measurements for a single crystal of Rh 17 S 15 with the superconducting transition temperature T C = 5.4 K. A pronounced elastic softening toward the T c under zero magnetic field was observed in the temperature dependence of the shear elastic constant C E = (C 11-C 12)/2, presumably due to the high density of states of d bands at the Fermi level E F. In the T dependence under several applied magnetic fields (H), the softening is gradually suppressed and the minimum shifts to the lower temperature side with increasing the H. From the results of various T and H scans, we summarized them in the magnetic phase diagram. We discuss the elastic properties and the mechanism of the elastic softening in terms of the electronic structure of Rh 17 S 15 in the vicinity of E F .