Ultrasonic shear velocity and attenuation of superconducting and non-superconducting SmBa2Cu3O7-δ (δ = 0.16 and 0.54)

Ultrasonic shear velocity, v s , and attenuation, α, of superconducting and non-superconducting SmBa 2 Cu 3 O 7-δ ( δ = 0.16 and 0.54) were measured between 80 and 200 K. A hardening trend was observed in both samples as the temperature was lowered. Shear velocity hysteresis was observed in both samples. However, the superconducting sample showed a larger hysteresis (80–200 K) compared with the non-superconducting sample (115–180 K). The superconducting sample showed 5% change in shear velocity, Δ v s v s , while the non-superconducting sample showed 2.2% change for the same temperature range. A pronounced increase in the shear velocity of the superconducting sample near the transition was observed while cooling down but not while warming up. The superconducting sample showed attenuation peaks at 85 K just below the transition temperature ( T c = 90 K) and also at 140 K. On the other hand, the non-superconducting sample did not show any attenuation anomaly, but a rapid decrease from 200 to 180 K followed by a gradual decrease as the temperature was lowered. The possible origins of ultrasonic attenuation peak and shear velocity anomalies observed in the superconducting and non-superconducting SmBa 2 Cu 3 O 7-δ are discussed in terms of oxygen orderings in the oxygen rich sample.