Low-lying unoccupied electronic states in 3d transition-metal fluorides probed by NEXAFS at the F 1s threshold
Publikation/Tidskrift/Serie: PHYSICAL REVIEW B
Förlag: American Physical Society
The near-edge x-ray absorption fine structure (NEXAFS) at the F 1s threshold has been studied with high-energy resolution for a series of binary fluorides, including KF, TiF4, VF4, VF3, CrF3, CrF2, MnF3, MnF2, FeF3, FeF2, CoF2, NiF2, CuF2, and ZnF2 as well as for SF6 in the gas phase, and for the PF6- and TiF62- molecular anions of the solid compounds KPF6 and K2TiF6. Most of these spectra were measured at the Russian-German beamline at BESSY II, while the spectra of KF and CuF2 were taken under comparable experimental conditions at the D1011 beamline at MAX-lab. The spectra of the solid samples were recorded via the total electron yield. The NEXAFS spectra were taken with the aim to elucidate the role of covalent bonding and its manifestation in x-ray absorption spectra as well as to gain information on the electronic structure of the conduction band along the whole series of 3d transition-metal (TM) fluorides. The spectra of these most ionic compounds of the 3d TM's have been analyzed in a comparative way considering also the F 1s NEXAFS spectrum of the molecular TiF62- anion in solid K2TiF6. In its turn, the latter spectrum has been interpreted by comparing with the F 1s NEXAFS spectrum of the molecular PF6- anion in KPF6 and that of SF6 in the gas phase. In this way, the low-lying empty electronic states of the 3d TM fluorides are shown to be formed by covalent mixing of the TM 3d with the fluorine 2p electronic states. It is further found that the number of low-lying empty electronic states with TM 3d-fluorine 2p hybridized character decreases gradually along the series of 3d TM fluorides, and is essentially zero in the case of ZnF2.
- Physics and Astronomy
- ISSN: 1098-0121