Using high-resolution O K-edge x-ray absorption near-edge- structure (XANES) spectroscopy, unoccupied states of the YxPr1-xBa2Cu3O7 (x=0-1) thin films and polycrystalline Pr1-xCaxBa2Cu3O7 (x=0-0.3) as well as R0.8Pr0.2Ba2Cu3O7 samples (R=Tm, Dy, Gd, and Sm) are investigated. In YxPr1-xBa2Cu3O7, hole numbers in the CuO2 planes decrease significantly with increasing Pr doping level. Hole carriers generated via Ca doping in Pr1-xCaxBa2Cu3O7 are directed predominantly into both the Zhang-Rice and Fehrenbacher- Rice (FR) states, while those in the CuO3 ribbons remain almost unchanged with Ca substitution. In R0.8Pr0.2Ba2Cu3O7, the hole content in the CuO2 planes decreases monotonically with increasing ionic size of the R3+ ions, confirming the hole depletion effect based on the Pr 4f-O 2p hybridization. We demonstrate the spectroscopic evidence of the existence of the FR states. The present XANES results provide a deeper understanding of the nature of hybridization and the origin of the ionic size effect.
|頁（從 - 到）||145021-145026|
|期刊||Physical Review B - Condensed Matter and Materials Physics|
|出版狀態||已發佈 - 2003 1月 1|
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