Low-temperature mechanical energy dissipation phenomena in lanthanum superconductors

Abstract

Abstract The anelastic properties of ceramics which belong to the lanthanum family of superconductors were studied. The internal friction and Young's modulus measurements were carried out by the vibrating reed technique in the temperature range from 20 to 300 K. The measurement frequency was in the range of 90–760 Hz. A large internal friction, corresponding to a maximum of the relaxation, was observed at a temperature about 50–60 K. An interesting correlation of both the peak height and the relaxation strength with the dopant content x has been found. An electronic relaxation phenomenon was considered as a possible source of the low-temperature internal friction maximum. The well known HTT→LTO phase transition was observed through both a pronounced change in Young's modulus and the internal friction maximum. Also the LTO→LTT phase transition was indirectly observed through an anomalous change in the Young's modulus.