Interrelation among superstructural ordering, oxygen nonstoichiometry, and lattice strain of double perovskite Sr2FeMoO6–δ materials

Double perovskite ceramics Sr2FeMoO6–δ having different amount of antisite disordering and oxygen content are prepared by the solid-phase reaction method using SrFeO2.52(3) and SrMoO4 initial reagents. X-ray and neutron diffraction techniques are used to estimate a modification in the structural parameters as a function of oxygen content and B–site cationic ordering. Reduction of oxygen content leads to an increase in the unit cell volume, which is mainly associated with an elongation of c –parameter of the tetragonal unit cell and relative expansion of the chemical bonds between Mo/Fe ions and apical oxygen ions. Superstructural ordering observed for the compounds causes a decrease in the unit cell volume, which is accompanied by a reduction in the length of the Mo/Fe – O bonds, located in the basal plane of oxygen octahedra. This modification of the unit cell parameters notably affects a character of the exchange interactions formed between B–site ions thus allowing to control magnetic and transport properties of Sr2FeMoO6–δ ceramics. It is found that comprehensive approach allows a consistent understanding of much debated structural/magnetic behaviors of double perovskite Sr2FeMoO6–δ systems, opening a venue for designing reliable devices based on the half-metallic double perovskite materials