Anomalous elastic response of HoBa2−xHoxCu3O7−δ ceramic superconductors

Anomalous elastic response has been observed in superconducting HoBa2−xHoxCu3O7−δ (x=0 and 0.15) from temperature dependent ultrasonic velocity measurements between 80 and 270 K. Longitudinal velocity of superconducting HoBa2Cu3O7−δ (Tc zero∼89 K) showed an anomaly around 230 K indicating a pronounced lattice stiffening. Superconducting HoBa1.85Ho0.15Cu3O7−δ (Tc zero∼70 K) also showed a similar longitudinal velocity anomaly around the same temperature. No anomaly was observed for oxygen-reduced non-superconducting HoBa2Cu3O7−δ. Temperature dependent shear velocity profiles and absolute velocity measurements at 80 K are also reported and the influence of oxygen content on elastic properties is discussed.