Resonant inelastic x-ray scattering (RIXS) is a powerful tool for determining the energy and symmetry of charge neutral electronic excitations in strongly correlated materials. We report on high-resolution polarization-dependent RIXS at the O 1s resonance of MnO and CoO. The experimental results are compared to multi-site cluster calculations, which are able to account for solid state effects and to describe collective excitations. Tuning the incident X-ray energy to the first absorption peak excites the O 1s electron into empty O 2p states strongly hybridized with the metal 3d states. Thus the de-excitation process reveals similar as in a study on NiO [1] contributions from low-energy excitations mediated by the O 1s core-hole. Apart from local oxygen ligand to metal charge transfer excitations and local crystal field excitations, the O 1s RIXS spectra give also rise to non-local metal-to-metal charge transfer excitations and double inter-site spin flip excitations (creating a double-singlet from two neighbouring triplets). Thereby the charge transfer energy Δ and the Hund coupling energy JH are probed.
[1] L.-C. Duda, T. Schmitt, M. Magnuson et al., Phys. Rev. Lett. 96, 067402 (2006). |