Structural and electromagnetic properties driven by oxygen vacancy in Sr2FeMoO6−δ double perovskite

Abstract

Nonstoichiometric Sr2FeMoO6−δ (δ = 0.132 and 0.296) double perovskite compounds have been synthesized by solid-state reaction. Effect of oxygen vacancy on its structural, magnetic and transport properties has been investigated by X-ray diffraction, magnetic and electronic transport measurements. Despite of different oxygen vacancy, both two compounds are of single phase and belong to the same space group, I4/m. Structural refinement shows that oxygen vacancy lowers the degree of ordering on B site and increases the lattice constant. Further structural analysis finds that owing to the oxygen vacancy, Fe atom is compressed, while the Mo atom changes from being compressed to being elongated. As predicted by the theoretical calculation, besides anti-site defects, oxygen vacancy is another important source for the lower Curie temperature of nonstoichiometric Sr2FeMoO6−δ. Meanwhile, the hopping integration of electron between Fe–O–Mo–O–Fe is reduced by oxygen vacancy, thus the resistivity and the semiconducting-metallic transition temperature of Sr2FeMoO6−δ are enhanced. However, the saturation magnetization (MS) of Sr2FeMoO6−δ at 5 K can be repeated well based on the ferrimagnetization model, suggesting that the anti-site defect is responsible for the reduction of MS, which is different from the literature results.