Ultrasonic-attenuation measurements in single-phasedYBa2Cu3O7

Ultrasonic attenuation at 15 MHz have been measured between 300 K and liquid-helium temperatures on a single-phased ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ sample with a 91-K superconducting transition temperature. The attenuation data show similarities to the behavior of heavy-fermion superconductors, with a local maximum just below $T_c$ and a nearly quadratic dependence of the attenuation at lower temperatures. At higher temperatures there is evidence for a relaxation maximum at 252 K, with an effective relaxation time of 1.1×${10}^{\mathrm{-}8}$ s.