X-ray absorption near-edge structure of Pr_1-xBa_2+xCu₃O₇

PrBa₂Cu₃O₇ (Pr123) has attracted much attention due to its non-superconductivity and other anomalies. The very recent reports on superconducting Pr123, instead of putting an end on this issue, virtually stimulate more controversies. One of the proposed explanations for the recently observed superconductivity in Pr123 is that the samples could be Ba-rich Pr123. To investigate this possibility, we have prepared Pr_1-xBa_2+xCu₃O₇ with x=0 to 0.3. It is found that resistivity of the samples becomes smaller with increasing x, together with elongation of the c-axis. O K-edge x-ray absorption structure indicates an increase in the carrier concentration with Ba doping. However, carriers are introduced in a peculiar way rather than simply added into CuO₂ planes.