Photoelectron study of the valence bands of some transition-metal fluorides

The results of a systematic photoelectron study using 40.81-eV photons of the valence bands of the transition-metal fluorides CrF₂, MnF₂, FeF₂, CoF₂, and NiF₂ are reported. Good agreement is found between the experimental values for the energy separation of the outermost levels of MnF₂, FeF₂, CoF₂, and NiF₂ and values calculated using the Born model for strongly ionic crystals. This agreement together with considerations of binding energy, relative photoionization cross sections, and F^-2p$ bandwidths allows an unambiguous assignment of the level ordering of the valence bands in the compounds studied. The level of smallest binding energy in each compound is derived from the $3d$ bands of the transition metal. Excellent agreement is found between the present ultraviolet-photoelectron-spectroscopy work and the published x-ray photoelectron spectra of ${FeF}₂$ and ${NiF}₂$. The present work also confirms the interpretation by Wertheim et al. of the spectrum of Fe${F}₂$.