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

Room-temperature Mn K-edge extended x-ray absorption fine structure (EXAFS) studies were carried out on La1-xSrxMnO3+delta (X = 0.1-0.9) compounds. It is found from the detailed EXAFS analysis that the local structure around Mn sites is different from the global structure inferred from x-ray diffraction, especially for x <= 0.4, indicating the presence of local distortions in MnO6 octahedra. For the rhombohedral compounds, x = 0.1 to 0.3, the distortion is 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 compounds with x = 0.4-0.8 two short bonds in the basal plane and four long bonds (two in the basal plane and the remaining two in the apical plane) are seen. For the compounds with compositions up to x = 0.3, the long bond length decreases and the short bond length increases with increase in x, whereas for the compounds with 0.4 <= x <=, 0.8 both types of bond length decrease. Such behaviour of bond lengths is an indication of the changed nature of distortion from Jahn-Teller type to breathing type at x = 0.4 composition.