Quantitative XANES Spectroscopy Study on the Prototype Hole- and Electron-Doped High-Tc Superconductor Systems, (La,Sr)2CuO4 and (Nd,Ce)2CuO4

Here we demonstrate that the Cu L-edge XANES (X-ray absorption near-edge structure) spectroscopy can be employed for quantitative analysis of the level of carrier-doping in the prototype hole- and electron-doped high-T-c superconductor systems, (La1-xSrx)(2)CuO4+delta and (Nd1-xCex)(2)CuO4+delta. The progress in hole-doping in the (La1-xSrx)(2)CuO4+delta system is seen as development of the shoulder peak (due to nominally trivalent copper) on the high-energy side of the main peak (due to nominally divalent copper) in the Cu L-3-edge region, whereas the progress in electron-doping in the (Nd1-xCex)(2)CuO4+delta system results in an additional absorption peak at about 934 eV (due to nominally monovalent copper), together with a decrease in the intensity of the main peak (due to nominally divalent copper). On the basis of these features, Cu-valence values are quantitatively obtained in excellent agreement with those calculated for the same samples from the precise oxygen contents, 4+delta, determined by means of wet-chemical analysis. The valence of Ce in (Nd1-xCex)(2)CuO4+delta is revealed to be somewhat lower than +4 (ca. +3.8) on the basis of Ce M-5-edge XANES data. In the O K-edge XANES spectra, the increase in the CuO2-plane hole concentration with increasing x in (La1-xSrx)(2)CuO4+delta is seen as an enhancement in the intensity of the pre-edge feature at similar to 528.9 eV. whereas for (Nd1-xCex)(2)CuO4+delta, no signs are observed that could be directly assigned to the change in electron-doping level.