X-ray-absorption studies of ${\mathrm{Nd}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Ce}}_{\mathit{x}}$${\mathrm{CuO}}_4$

O K-edge absorption studies of Ce-doped ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$ using both total electron yield and fluorescence emission show similar features to undoped ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$. This is in contrast to that observed for Sr-doped ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$ and ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$. In addition, M-edge absorption spectra of Ce and Nd show that Ce ions are in an intermediate valence state and Nd remains in the trivalent state. Results are presented and discussed along with those of other Cu oxide superconductors.