Abstract
X-ray absorption near-edge structure (XANES) data for the PrBa 2 Cu 3 O 7-y (6.21 ≤ 7-y ≤ 6.95 insulating system with anomalous Pr antiferromagnetic order are reported. Pr L 3 -edge XANES indicates that Pr formal valence decreases from 3.17-3.18 for oxygenated samples to 3.09 for oxygen-depleted PrBa 2 Cu 3 O 6.43 , 3.03 for PrBa 2 Cu 3 O 6.38 and 3.01 for PrBa 2 Cu 3 O 6.21 . The variation of Pr valence indicates that the doped holes initially stay in the CuO 1-y plane and contribute to Cu(I)-Cu(II) transformation in this plane, but gradually move into the CuO 2 bi-layers with PrO 8 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 PrBa 2 Cu 3 O 6.95 . The small average Cu formal valence or large Pr formal valence is closely related to the absence of superconductivity.