Electronic excitations around the substituted atom in La2Cu1 -yNiyO4 as seen via resonantinelastic x-ray scattering

We perform a resonant inelastic x-ray scattering (RIXS) study of Ni-substituted La{sub 2}CuO{sub 4} and Cu-substituted La{sub 2}NiO{sub 4}. Resonantly enhanced charge-transfer excitations are successfully observed by tuning the incident photon energy to the K edge of the substituted element. These excitations display a very weak momentum dependence, evidencing their local character. We find a shift in the energy of the onset edge of these features compared with the nonsubstituted compounds La{sub 2}CuO{sub 4} and La{sub 2}NiO{sub 4}. This shift is quantitatively reproduced by exact diagonalization calculations of the RIXS spectra. RIXS is shown to be a powerful tool to probe the electronic states of substituted elements and to understand their interaction with surrounding atoms.