Charge transfer and Mott-Hubbard excitations in FeBO3: An FeK-edge resonant inelastic x-ray scattering study

Abstract

Momentum-resolved resonant inelastic x-ray scattering (RIXS) spectroscopy has been carried out at the Fe K edge, successfully for the first time. The RIXS spectra of a FeBO3 single crystal reveal a wealth of information on 1 − 10 eV electronic excitations. The IXS signal resonates both when the incident photon energy approaches the pre-edge (1s-3d) and the main-edge (1s-4p) of the Fe K edge absorption spectrum. The RIXS spectra measured at the pre-edge and the mainedge show quantitatively different dependences on the incident photon energy, momentum transfer, polarization, and temperature. Electronic excitations observed in the pre-edge and main-edge RIXS spectra are interpreted as Mott-Hubbard (MH) and charge-transfer (CT) excitations, respectively. The charge-transfer gap ∆ G = 3.81 ± 0.04 eV and the Mott-Hubbard gap U G = 3.96 ± 0.04 eV, are determined, model independently from the experimental data. The CT and MH excitations are assigned using molecular orbitals (MO) in the cluster model and multiplet calculation in the many-electron multiband model, respectively.

Effect of Fe-substitution on the structure and magnetism of single crystals Mn2-xFexBO4

“…The separation of these two peaks was found to be 10Dq = 1.30 ± 0.05 eV. We noted that this parameter is in good agreement with those reported for FeBO 3 10Dq = 1.4 eV from RIXS data [27]. Figure 7a presents the normalized Mn K-edge XANES spectra and their first derivatives for the Mn 2 BO 4 sample has been also measured as an example of manganese mixed-valence state in the warwickite structure.…”

Simulations of valence excited states in coordination complexes reached through hard X-ray scattering

“…K-edge RIXS has been successfully used to probe d-d excitations in several systems. 21,24,25 The current spectra are dominated by dipole-allowed LMCT transitions and d-d excitations have not been identified. The reason is that for direct RIXS in a centrosymmetric complex, both absorption and emission processes (1s -3d-1s) are electric-dipole forbidden, and the scattering intensity is very low.…”

“…Hard X-ray RIXS has been extensively used to probe both metal-centered and metal-ligand excitations. 3,[15][16][17][18][19][20][21][22][23][24][25][26] In direct RIXS, excitation is made directly into the metal K pre-edge (1s -3d), 21,[23][24][25]27 which can in itself be used to understand both geometric and 3d-orbital electronic structure. 28 The experiment is challenging due to relatively low photon counts.…”