Altering the valence state of cations without cation non-stoichiometry usually occurs in compounds with multiple valance states, where oxygen vacancies are often charge-compensated by the change of cation valence state24. Perovskite oxides with transition metals such as V, Co, Fe, and Mn belong to this category. SrFeO3−δ is an example of this type. The existence of multiple valence states of Fe allows for various stable states of oxygen occupancy in the lattice. Much of the recent attention in SFO thin films stems from the strong dependence of the crystal structure, magnetic and electrical properties of this material on the oxygen content (0 ≤ δ ≤ 0.5). SrFeO2.5 can exhibit semiconducting behavior and brownmillerite structure, while cubic perovskite SrFeO3 has been shown to exhibit metallic behavior with existence of helical antiferromagnetic-ordered spin structure252628.