Coexistence of ferroelectricity and ferromagnetism in fluorine-doped barium titanate at room temperature

Barium titanate (BaTiO3, BTO) is considered to be a typical room temperature ferroelectric. We have fabricated fluorinated BTO (BTOF) polycrystalline ceramics by using NH4F as doping compounds, in which one fluorine substitutes for one oxygen. At room temperature, the BTOF samples retain the tetragonal ferroelectric crystal structure, but change toward cubic paraelectric phase with F increasing. However, the difference in charge between O2− and F− anions makes the Ti3+ arise in BTOT ceramics. The coexistence of ferroelectricity and ferromagnetism was observed in BTOF ceramics at room temperature by P–E loop and M–H loop. Moreover, these two ferroic orders originate from the Ti atoms. This work presents an alternative scheme for exploring multiferroic materials with large polarization and magnetization at room temperature, and we also expect preferable magnetoelectric coupling.