STRUCTURAL INSTABILITY OF Y_(1-x)Pr_xBa_2Cu_3O_(7-δ) SUPERCONDUCTORS STUDIED BY POSITRON ANNIHILATION LIFETIME

摘要

The temperature dependence of the positron annihilation lifetime in high-quality, single-phase Y_(1-x)Pr_xBa_2Cu_3O_(7-δ) has been measured from 78 to 300K for a better understanding of the origin of the normal state anomaly observed in high T_C superconductivity studies. The normal state anomaly has been detected around 30 to 40K above T_C for the samples with x=0.0 and 0.1, but, it was not found for the sample with x=0.2 where T_C is lower than 80K. The experimental results show that the phase transition-like behavior caused by the structural instability results in the normal state anomaly which acts as a the precursor of high T_C superconductivity.