Influence of local structure on magnetic properties of layered cobaltites PrBaCo2O(5+δ), δ > 0.5.

The effect of local structure on the magnetic and transport properties of the layered perovskites has been investigated. The samples PrBaCo(2)O(5+δ), (δ = 0.80 and 0.67) crystallize in the same 112 type tetragonal structure but have different magnetic ground states. Extended x-ray absorption fine structure (EXAFS) spectroscopy has been employed to explain the changes in magnetic interactions based on the rotation and tilting of CoO polyhedra in these oxygen-rich double perovskites.

Local structure of Pt and Pd ions in Ce(1-x)TixO2: x-ray diffraction, x-ray photoelectron spectroscopy, and extended x-ray absorption fine structure.

Ce(1-x-y)Ti(x)Pt(y)O(2-delta) (x=0.15; y=0.01) and Ce(1-x-y)Ti(x)Pd(y)O(2-delta) (x=0.25; y=0.02 and 0.05) are found to be good CO oxidation catalysts [T. Baidya et al., J. Phys. Chem. B 110, 5262 (2006); T. Baidya et al., J. Phys. Chem. C 111, 830 (2007)]. A detailed structural study of these compounds has been carried out by extended x-ray absorption fine structure along with x-ray diffraction and x-ray photoelectron spectroscopy. The gross cubic fluorite structure of CeO(2) is retained in the mixed oxides. Oxide ion sublattice around Ti as well as Pt and Pd ions is destabilized in the solid solution. Instead of ideal eight coordinations, Ti, Pd, and Pt ions have 4+3, 4+3, and 3+4 coordinations creating long and short bonds. The long Ti-O, Pd-O, and Pt-O bonds are approximately 2.47 A (2.63 A for Pt-O) which are much higher than average Ce-O bonds of 2.34 A.