EXAFS STUDIES OF CHANGES IN THE LOCAL ENVIRONMENT OF CU IONS IN FE- AND ZN-DOPED YBA2CU3O7-DELTA SUPERCONDUCTOR

EXAFS spectra have been measured at the Cu K edge in Fe- and Zn-doped YBa2Cu3O7-delta using a laboratory EXAFS Spectrometer. The dopant concentration was varied and the changes in the near-neighbour environment around the Cu ions were examined by determining the best-fit structural parameters after curve fitting to the first-shell EXAFS function. The average Cu-O distance is found to decrease as Fe concentration increases, and is found to increase as Zn concentration increases. The results indicate that Fe and Zn affect the Cu-O environment significantly but in different ways. The mobile hole concentration in the YBa2Cu3O7-delta superconductor is known to change with doping, and our results indicate that the Cu-O distance and the mobile hole concentration are probably related, the Cu-O distance increasing as mobile hole concentration decreases and vice versa.