Overlap of Cu3d and F2p orbitals and low-energy excitations in KCuF3 studied by polarization-dependent x-ray absorption and emission spectroscopy

Site-, elemental-, and orbital-resolved partial density of states in KCuF3 single crystal have been obtained by polarization-dependent x-ray absorption and emission spectroscopy measurements across the FK -edge and ab initio full-multiple-scattering cluster calculations. The FK x-ray absorption spectroscopy spectra show well-defined polarization dependence. The measurements reveal strong overlap between Cu3d and F2p states and identify clearly the F2 pz and F2 px,y empty states created at different F sites. The calculations, performed for the nonequivalent F sites in the structure, confirm the energy overlap, the charge transfer between Cu3d and F2p states, and the different F2p-Cu3d overlap for the two nonequivalent F sites of KCuF3. Across the FK edge, resonant x-ray emission spectroscopy detects a broad peak due to d-d excitations centered at about 1.2-1.6 eV and an intense charge-transfer-like transition around 7 eV. © 2009 The American Physical Society.