Influence of vacuum annealing on microstructure and magnetic properties of (Ba0.8Sr0.2)(Ti0.3Fe0.7)O3 ceramic

Fe-doped (Ba0.8Sr0.2)TiO3 ceramic was prepared by solid-state reaction, and room-temperature ferromagnetism was achieved via vacuum annealing. The effect of annealing on microstructure, magnetic properties and exchange mechanism was investigated using X-ray diffraction, Mössbauer spectroscopy, and vibrating sample magnetometer. The as-prepared and annealed samples are shown to be monophasic, crystallizing in a 6H-BaTiO3-type hexagonal perovskite structure. The paramagnetism is exhibited in the as-prepared state, arising from the super-exchange interactions of Fe3+ on tetrahedral and octahedral Ti sites. On the other hand, vacuum annealing is proved to be a feasible way for Fe-doped (Ba1−xSrx)TiO3 to obtain ferromagnetism via modifying the Fe occupational distribution. The super-exchange interactions between Fe3+ on pentahedral and octahedral Ti sites lead to the room-temperature ferromagnetism observed in the annealed sample.