Determination of valence state of Mn ions in Pr1−xAxMnO3−δ (A = Ca, Sr) by Mn-L3 X-ray absorption near-edge structure analysis

Abstract

The valence states of the Mn ions in Pr1−xAxMnO3−δ (A=Ca, Sr) are investigated by Mn-L3 X-ray absorption near-edge structure (XANES) analysis. The spectral fine structures in the Mn-L3 XANES analysis show a significant difference between Pr0.5Ca0.5MnO3−δ and Pr0.5Sr0.5MnO3−δ, a paramagnetic insulator and a ferromagnetic metal, respectively, at room temperature, whereas the spectral structures of Pr0.7Ca0.3MnO3−δ and Pr0.7Sr0.3MnO3−δ, paramagnetic insulators, are almost identical. These results indicate that the valence states of the Mn ions in these materials are highly correlated with their magnetic and electrical properties. A significant difference was also found between the Mn-L3 XANES profiles of Pr1−xCaxMnO3−δ and the profiles formed by the linear combination of the Mn-L3 XANES spectra of PrMnO3 (Mn3+) and CaMnO3 (Mn4+). This difference indicates that the Mn ions in these materials do not have a mixed-valence state of 3+ and 4+, but have an intermediate valence state o 3+ and 4+.