Ruimin Qiao, Timothy Chin, Stephen J. Harris, Shishen Yan, Wanli Yang
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 change, with an order of magnitude larger in energy, between divalent and trivalent compounds is attributed to the spin exchange stabilization of half- filled 3d system, which is much enhanced in the ionic fluoride system. This work provides the spectroscopic foundation for further studies of complicated Mn compounds for practical applications.
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http://arxiv.org/abs/1208.6319
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