The role of the dopants and oxygen vacancies in the magnetic response of Fe-doped and (Fe, Sn) co-doped SrTiO₃ perovskite oxide

In this work we present a combined theoretical and experimental study of the structural, magnetic, and hyperfine properties of Fe doped and (Fe, Sn) co-doped SrTiO₃ perovskite (STO). ⁵⁷Fe-Mössbauer spectroscopy (⁵⁷Fe-MS) was employed to determine the hyperfine interactions at the Fe sites of doped STO for different Fe and Sn concentrations. The theoretical study was performed in the framework of the Density Functional Theory (DFT) using the full-potential linearized augmented plane wave (FP-LAPW) method. The effect of the oxygen vacancies on the magnetic and hyperfine properties and on the magnetic alignment of Fe and Sn impurities was studied. The combination of the DFT calculations, considering different structural models for doped-STO, and ⁵⁷Fe-MS enable us to obtain a structural characterization of Fe-doped and (Fe, Sn) co-doped STO and to explain the origin of the observed hyperfine interactions and the magnetic signal.