Short- and long-range order in La1−xSrxCoO3 and La1−xBaxCoO3

The short- and long-range order correlations of the crystal structure in the distorted perovskites La1−xSrxCoO3 and La1−xBaxCoO3 (0.0⩽x⩽0.5) have been studied by the neutron powder diffraction (NPD) and the Co K-edge X-ray absorption spectroscopy (XAS) measurements. The results of XAS and NPD indicate a local distortion around the Co3+ ions in LaCoO3 at room temperature. The substitution of the La3+ ions by the Sr2+(Ba2+) ions leads to a gradual increase of the Co–O–Co angle and is accompanied by an increase of the mean square relative displacement (MSRD) of the Co–O bond. These results correlate with an increase of the oxygen amplitude vibration in the direction perpendicular to the Co–O bond. The possible explanation of the observed changes of the crystal and electronic structures in the above-mentioned cobaltites is discussed.