Double-perovskite oxides have attracted recent attention due to their attractive functionalities and application potential. In this paper, we demonstrate the effect of dual controls, i.e., the deposition pressure of oxygen (PO2) and lattice mismatch (ε), on tuning magnetic properties in epitaxial double-perovskite Sr2FeReO6 films. In a nearly lattice matched Sr2FeReO6/SrTiO3 film, the ferrimagnetic-to-paramagnetic phase transition occurs when PO2 is reduced to 30 mTorr, probably due to the formation of Re4+ ions that replace the stoichiometric Re5+ to cause disorders of B-site ions. On the other hand, a large compressive strain or tensile strain shifts this critical PO2 to below 1 mTorr or above 40 mTorr, respectively. The observations can be attributed to the modulation of B-site ordering by epitaxial strain through affecting elemental valence. Our results provide a feasible way to expand the functional tunability of magnetic double-perovskite oxides that hold great promise for spintronic devices.
Keywords: double perovskites; epitaxial strain; magnetism; oxide heterostructures.