Multiferroic and magnetoelectronic polarizations in BaFe12O19 system

Coexistence of ferroelectricity and ferromagnetism in one single phase of a solid is of great interest because of the potential application for novel electronic devices. We report on the enhanced ferroelectricity jointly co-existing with excellent magnetic performance in M-type barium hexaferrite (BaFe₁₂O₁₉), which demonstrating a classic electric polarization (P-E) hysteresis loop with full saturation. Two nonlinear current peaks in the I–V curve for polarization switch and giant abnormal change of dielectric constant near Curie temperatures provide sufficient experimental evidences to verify the ferroelectricity of BaFe₁₂O₁₉ ceramics. It holds a large remnant polarization of 55.7 μC/cm² and a suitable coercive field at 441 kV/cm. Two peaks at 194 °C and 451 °C in the temperature-dependent dielectric spectrum of BaFe₁₂O₁₉ ceramics are considered to be the phase transition from ferro-to antiferro- and antiferro-to para-electric structures. A conventional strong magnetic hysteresis loop was also observed. The influence of oxygen vacancies on the band structure, electric and magnetic properties has been discussed in detail. The magnetically induced E-polarization upon the BaFe₁₂O₁₉ ceramics was achieved in the form of alternating spin current waves. These combined multiple functional responses of large ferroelectrics and strong ferromagnetism reveal the excellent multiferroic features of BaFe₁₂O₁₉, which would bring forth the great opportunity to create novel electric devices with active coupling effect between magnetic and electric orders.