Structure, electrical and magnetic property investigations on dense Fe-doped hexagonal BaTiO3

Hexagonal Ba(Ti1−xFex)O3−δ (x = 1/6, 1/3) ceramics treated with post annealing are specifically synthesized to explore the origin mechanism of the unusual ferromagnetism in the doped system. X-ray diffraction refinements and transmission electron microscope experiments reveal that their structures are incommensurately modulated owing to simultaneous oxygen vacancies at both O1 and O2 sites. Consequently, coexisting weak ferrielectricity and weak ferromagnetism are presented at room temperature. Analysis on their leakage current plot reveals that their conduction follows trap-filled limit model. In combination with the magnetism studies on 5 mol% Fe-doped crystals [Phys. Rev. B 83, 144407 (2011)], the reduction of ferromagnetism with an increase of conductivity suggests that dynamic exchanges of trapped electrons among the bound magnetic polarons attribute to the intrinsic ferromagnetism.