Spectroscopic fingerprints of valence and spin states in manganese oxides and fluorides

TL;DR

This study systematically analyzes soft X-ray absorption spectra of manganese oxides and fluorides, revealing how spectral features relate to valence and spin states, and establishing a foundation for future research on complex Mn compounds.

Contribution

It provides a comprehensive spectroscopic analysis linking Mn valence and spin states to specific spectral features across various compounds, including oxides and fluorides.

Findings

Mn-L spectra reliably indicate Mn valence and spin states.

Distinct pre-edge features enable quantitative molecular orbital analysis.

Edge shifts correlate with Mn oxidation and spin states, especially in fluorides.

Abstract

We performed a systematic study of soft X-ray absorption spectroscopy in various manganese oxides and fluorides. Both Mn L-edges and ligand (O and F) K-edges are presented and compared with each other. Despite the distinct crystal structure and covalent/ionic nature in different systems, the Mn-L spectra fingerprint the Mn valence and spin states through spectral lineshape and energy position consistently and evidently. The clear O- and F- K pre-edge features in our high resolution spectra enable a quantitative definition of the molecular orbital diagram with different Mn valence. In addition, while the binding energy difference of the O-1s core electrons leads to a small shift of the O-K leading edges between trivalent and quadrivalent manganese oxides, a significant edge shift, with an order of magnitude larger in energy, was found between divalent and trivalent compounds, which is attributed to the spin exchange stabilization of half- filled 3d system. This shift is much enhanced in the ionic fluoride system. This work provides the spectroscopic foundation for further studies of complicated Mn compounds.