Magnetic properties dependence on Fe2+/Fe3+ and oxygen vacancies in SrTi0.95Fe0.05O3 nanocrystalline prepared by hydrothermal method

•SrTi1−xFexO3 (x = 0–0.20) nanoparticles were prepared by hydrothermal method.•As-prepared samples exhibit different types of magnetic behaviors.•Annealing can increase Fe2+/Fe3+, oxygen vacancy and magnetization (Ms).•All annealed samples exhibit ferromagnetic behavior.•Fe2+–VO2−–Fe2+ and Fe3+–VO2−–Fe3+ couplings are proposed for the increase of Ms.

SrTi1−xFexO3 (x = 0, 0.05, 0.10, 0.15 and 0.20) nanoparticles were synthesized by hydrothermal method. SrTi0.95Fe0.05O3 samples were annealed at 500, 600 and 700 °C in Ar. X-ray diffraction (XRD) results indicate a perovskite structure of all as-prepared and annealed samples with the impurity phase of SrCO3 and Fe3O4 in as-prepared samples of x > 0.10. SEM micrograph of as-prepared SrTi0.95Fe0.05O3 reveals an agglomeration of nanoparticles. TEM image shows a cubic shape of as-prepared SrTi0.95Fe0.05O3 nanoparticles with an average size of 60.2 nm. X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS) results of all annealed SrTi0.95Fe0.05O3 samples reveal, respectively the increasing of Fe2+ cations and oxygen vacancies. Magnetic properties of as-prepared and all annealed samples were measured using the vibrating sample magnetometer (VSM). Pure SrTiO3 exhibits diamagnetic behavior, whereas as-prepared SrTi1−xFexO3 (x = 0.05 and 0.10) samples exhibit ferromagnetic behavior and those of x = 0.15 and 0.20 are paramagnetic. All annealed SrTi0.95Fe0.05O3 samples are ferromagnetic due to the F-center exchange (FCE) coupling interactions of Fe2+–VO2−–Fe2+ and Fe3+–VO2−–Fe3+, resulting in the maximum magnetization value of 0.02 emu/g for SrTi0.95Fe0.05O3 sample annealed at 700 °C.

Graphical abstractMagnetizations of annealed SrTi0.95Fe0.05O3 nanoparticles at 500, 600 and 700 °C in Ar for 3 h. The increase of annealing temperature can increase the cations ratio of Fe2+/Fe3+ and oxygen vacancy, resulting in the increase of saturation magnetization due to the existence of the Fe2+–VO2−–Fe2+ coupling more than that of the Fe3+–VO2−–Fe3+.Figure optionsDownload full-size imageDownload as PowerPoint slide