Abstract
The electronic and magnetic excitations of bulk NiO have been determined using the to crystal-field transition at the Ni edges with resonant inelastic x-ray scattering at 66.3- and 67.9-eV photon energies and 33-meV spectral resolution. Unambiguous assignment of the high-energy side of this state to a spin-flip satellite is achieved. We extract an effective exchange field of meV in the excited final state from empirical two-peak spin-flip model. The experimental data is found consistent with crystal-field model calculations using exchange fields of 60–100 meV. Full agreement with crystal-field multiplet calculations is achieved for the incident photon energy dependence of line shapes. The lower exchange parameter in the excited state as compared to the ground-state value of 120 meV is discussed in terms of the modification of the orbital occupancy (electronic effects) and of the structural dynamics: (A) With pure electronic effects, the lower exchange energy is attributed to the reduction in effective hopping integral. (B) With no electronic effects, we use the Heisenberg model of antiferromagnetism to derive a second-nearest-neighbor exchange constant = meV. Based on the linear correlation between and the lattice parameter from pressure-dependent experiments, an upper limit of 2% local Ni-O bond elongation during the femtosecond scattering duration is derived.
- Received 1 December 2021
- Revised 4 March 2022
- Accepted 19 May 2022
DOI:https://doi.org/10.1103/PhysRevB.106.035104
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Published by the American Physical Society