Ultrasonic anomalies in n-type superconducting Nd2−xCexCuO4−y compounds

Ultrasonic measurements were carried out on a series samples of Nd 2−x Ce x CuO 4−y with x ranged from 0 to 0.2. The anomalous changes in both attenuation and velocity around 190 to 200 K were found for the superconducting samples (x=0.15) during cooling, whereas no anomalies can be found in this region for non-superconducting samples. The implications of this phenomenon is discussed.