Pressure-dependent electronic structures and orbital hybridization of Mn 3d states in multiferroic BiMnO3: A combined x-ray absorption, x-ray emission, and resonant x-ray emission study

We investigated both the dependence of electronic structures and spin states on pressure up to 25 GPa and the hybridization of Mn 3d states in BiMnO3 by combining measurements of x-ray absorption, x-ray emission, and 1s3p-resonant x-ray emission spectroscopy (RXES). The Mn K-edge x-ray absorption spectra of BiMnO3 show a great change for pressure similar to 1 GPa, corresponding to the occurrence of a structural transition. The gradually diminished shoulder of the white line and subsequently increased intensity of the white line of Mn K-edge spectra on increasing the external pressure from 2 to similar to 15 GPa are attributed to a diminished Jahn-Teller distortion of MnO6 octahedra in BiMnO3 with increasing pressure. For pressure >similar to 15 GPa, the intensity of the white line in Mn K-edge spectra of BiMnO3 became progressively decreased. Preedge peaks in Mn K-edge spectra of BiMnO3 at P = 25 GPa shifted to smaller energy similar to 0.3 eV relative to P = 0.7 GPa. The spin magnetic moments deduced from the K beta emission line show a significant decrease for pressures between 0 and 2 GPa, then a monotonic decrease for pressures between 2 and 7 GPa, and a slight decrease after 7 GPa. The 1s3p-RXES spectra obtained at the Mn-K preedge for BiMnO3 reveal that the empty Mn 3d(e(g)(0)) states exhibit a delocalized character, suggested to originate from the hybridization of the unoccupied Mn 3d states with the Mn 4p orbitals. These findings provide insight into the evolution of electronic structures related to the structural transformation of multiferroic BiMnO3 under pressure.