Local distortion of MnO6 octahedron in La1−xSrxMnO3+δ (x = 0.1–0.9): an EXAFS study

Abstract

Room-temperature Mn K-edge extended x-ray absorption fine structure (EXAFS) studies were carriedout on La1−xSrxMnO3+δ (x = 0.1–0.9) compounds. It is found from the detailed EXAFS analysis that the local structure aroundMn sites is different from the global structure inferred from x-ray diffraction, especially forx≤0.4, indicating the presence of local distortions inMnO6 octahedra. For the rhombohedral compounds,x = 0.1 to 0.3, the distortionis maximum for x = 0.1 and two bond lengths are seen: a short one in the basal plane and a long one in the apical plane. For compoundswith x = 0.4–0.8 two short bonds in the basal plane and four long bonds (two in the basal plane and theremaining two in the apical plane) are seen. For the compounds with compositions up tox = 0.3, the long bond length decreases and the short bond length increases with increase inx, whereas for thecompounds with 0.4≤x≤0.8 both types of bond length decrease. Such behaviour of bond lengths is an indicationof the changed nature of distortion from Jahn–Teller type to breathing type atx = 0.4 composition.