Epitaxial thin films of multiferroic Bi₂FeCrO₆ with B-site cationic order

Epitaxial thin films of Bi₂FeCrO₆ (BFCO) have been synthesized by pulsed laser deposition on SrRuO₃ on (100)- and (111)-oriented SrTiO₃ substrates. Detailed x-ray diffraction and cross-section transmission electron microscopy analysis revealed a double perovskite crystal structure of the BFCO epitaxial films very similar to that of BiFeO₃ along with a particularly noteworthy Fe³⁺/Cr³⁺ cation ordering along the [111] direction. The films contain no detectable magnetic iron oxide impurities and have the correct cationic average stoichiometry throughout their thickness. They however exhibit a slight modulation in the Fe and Cr compositions forming complementary stripe patterns, suggesting minor local excess or depletion of Fe and Cr. The epitaxial BFCO films exhibit good ferroelectric and piezoelectric properties, in addition to magnetic properties at room temperature, as well as an unexpected crystallographic orientation dependence of their room-temperature magnetic properties. Our results qualitatively confirm the predictions made using the ab initio calculations: the double perovskite structure of BFCO films exhibit a Fe³⁺/Cr³⁺ cation ordering and good multiferroic properties, along with the unpredicted existence of magnetic ordering at room temperature.