Hole states in Eu0.9-xPrxCa0.1BaSrCu3O7-delta studied by X-ray absorption spectroscopy

The hole states located on different oxygen sites have been investigated in Eu0.9-xPrxCa0.1BaSrCu3O7-delta with increasing Pr3+ substitution by high-r esolution oxygen K-edge and copper L-edge X-ray absorption spectra. The res ults reveal that the hole states are depleted systematically by the substit ution and in turn lead to a reduction in T-c. However, the rate at which th e depletion occurs is lower in Eu0.9-xPrxCa0.1BaSrCu3O7-delta compared to t hat in Y1-xPrxBa2Cu3O7-delta and Dy1-xPrxBa2Cu3O7-delta. This is due to the partial substitution of Ba2+ by Sr2+ ions and R (rare earth element) by Ca 2+ ions in the present case. The depletion of hole states gives evidence in support of the hole-depletion models based on Pr 4f-O 2p(pi) hybridization . The possible reasons for the anomalous behavior of Pr3+ ions in RBa2Cu3O7 -delta are also discussed.