X-ray-edge studies and photoemission of MnxSn1-xMo6S8

X-ray-absorption and -photoemission studies were carried out on the manganese-doped Chevrel-phase compound MnxSn1-xMo6S8 for x=0.1, where a maximum superconducting transition temperature Tc occurs. With use of synchrotron radiation and x-ray fluorescence, near-edge-absorption and extended x-ray-absorption fine-structure (EXAFS) spectra were obtained at the K edge of Mn in the doped compound. The results indicate that each manganese atom, surrounded by eight sulfur atoms, substitutes for tin at the center of a large cavity in SnMo6S8. The manganese-sulfur nearest-neighbor distance is found to be 2.02±0.05 A, somewhat less than 2.26 A for Sn in SnMo6S8. The probable charge of manganese is found to be 4+ and, considering the valence-electron- charge model of charge transfer, this explains the observed maximum in Tc. The photoemission experiments yield an energy distribution curve for the valence band which is in good agreement with band theory.