Determination of B-site ordering and structural transformations in the mixed transition metal perovskites La2CoMnO6and La2NiMnO6

The low-and high-temperature structures of La 2 CoMnO 6 and La 2 NiMnO 6 have been refined using powder neutron diffraction. At low temperatures the materials adopt a charge-ordered monoclinic structure which transforms to a rhombohedral structure at elevated temperature without loss of charge ordering. This charge ordering scheme allows us for the first time to rationalize the relationships between the physical and structural properties of these materials.