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

Abstract

The hole states located on different oxygen sites have been investigated in Eu0.9 – xPrxCa0.1BaSrCu3O7 – δ with increasing Pr3+ substitution by high-resolution oxygen K-edge and copper L-edge X-ray absorption spectra. The results reveal that the hole states are depleted systematically by the substitution and in turn lead to a reduction in Tc. However, the rate at which the depletion occurs is lower in Eu0.9 – xPrxCa0.1BaSrCu3O7 – δ compared to that in Y1 – xPrxBa2Cu3O7 – δ and Dy1 – xPrxBa2Cu3O7 – δ. This is due to the partial substitution of Ba2+ by Sr2+ ions and R (rare earth element) by Ca2+ ions in the present case. The depletion of hole states gives evidence in support of the hole-depletion models based on Pr 4f–O 2pπ hybridization. The possible reasons for the anomalous behavior of Pr3+ ions in RBa2Cu3O7 – δ are also discussed.