Abstract
Ultrasonic shear velocity and attenuation measurements on superconducting ( δ∼0.02) and non-superconducting ( δ∼0.45) polycrystalline EuBa 2Cu 3O 7- δ have been performed at 7-8 MHz between 80 K and 220 K. Enhanced attenuation and softening tendency was observed near 170 K in the superconducting material. The attenuation peak is greatly suppressed and no softening tendency was observed in the non-superconducting sample. The reduction of oxygen content from O 6.98 to O 6.55 caused the absolute shear velocity to decrease. The O 6.98 sample showed a 2.25% change in shear velocity between 80 K and 220 K while the O 6.55 sample showed a 3.75% change within the same temperature range. These anomalies are discussed in terms of possible oxygen ordering. The acoustic Debye temperature of the superconducting sample in the void-free approximation is estimated to be Θ D∼457 K.
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