Anomalous Pr ordering, Pr L3-edge and Cu K-edge XANES studies for the insulating PrBa2Cu3O7-y system

[[abstract]]X-ray absorption near-edge structure (XANES) data for the PrBa2Cu3O7-y (6.21⩽7-y⩽6.95) insulating system with anomalous Pr antiferromagnetic order are reported. Pr L3-edge XANES indicates that Pr formal valence decreases from 3.17-3.18 for oxygenated samples to 3.09 for oxygen-depleted PrBa2Cu3O6.43, 3.03 for PrBa2Cu3O6.38 and 3.01 for PrBa2Cu3O6.21. The variation of Pr valence indicates that the doped holes initially stay in the CuO1-y plane and contribute to Cu(I)-Cu(II) transformation in this plane, but gradually move into the CuO2 bi-layers with PrO8 cage and result in the appearance of Pr (IV) localized-hole state with increasing oxygen content. Cu K-edge XANES indicates that the average Cu formal valence increases from less than 2 in oxygen-depleted region to a value larger than 2 for oxygenated samples, with the estimated Cu valence of 2.24 for PrBa2Cu3O6.95. The small average Cu formal valence or large Pr formal valence is closely related to the absence of superconductivity[[fileno]]2010102010220[[department]]物理