Anomaly of local structure of La[sub 0.7]Ca[sub 0.3-x]Ba[sub x]MnO[sub 3] manganites at Curie temperature.

The local structure of La[SUB0.7]Ca[SUB0.3-x]Ba[SUBx]MnO[SUB3] (x = 0; 0.03; 0.06;...; and 0.3) lanthanum manganites were studied by extended x-ray absorption fine structure analysis. Dispersion, σ[SUP2][SUBMn-O], and asymmetry, σ[SUP3][SUBMn-O], of the pair distribution function for the Mn-O bond distances of MnO[SUB6] octahedron showed a maximum on x dependence. The maximum of σ[SUP2][SUBMn-O] is caused by an increase of dynamic displacements of the Mn-O bond distances near the Curie temperature, T[SUBC]. The observed x dependence of σ[SUP3][SUBMn-O] is caused by a reduction in mobility of the charge carriers approaching T[SUBC] from low as well as high temperatures. [ABSTRACT FROM AUTHOR]