Pressure-induced spin transition and evolution of the electronic excitations of FeBO3: Resonant inelastic x-ray scattering results

A high-pressure resonant inelastic x-ray scattering (RIXS) of at the Fe K pre-edge has been carried out to study the evolution of electronic excitations through the pressure-induced spin transition. Systematic peak shifts with insignificant peak width change are observed with increasing pressure in the high-spin state. An electronic transition occurs in tandem with the high-spin to low-spin transition, observed as the emergence of multiple new low-energy peaks in the spectra. The energy gap is reduced due to these low-energy peaks, not a peak width broadening. The observed electronic excitations are associated with dd excitations, which are calculated using a full-multiplet theory. We consider changes in crystal-field splitting and covalency to explain the observed peak shifts in the high-spin state. The new peaks that emerge upon the high-to low-spin transition are compared with dd excitations for the low-spin configuration.