Direct magnetoelectric coupling from magnetically/ferroelectrically active cation in low-symmetry octahedron

Achieving direct and large magnetoelectric (ME) coupling in single-phase multiferroic at room temperature is a challenging task for physicists and material engineers as type I multiferroics have independent ferroic orders and type II multiferroics exhibit fairly weak polarization due to spin-orbit interaction at very low temperatures. Here, we show that by lowering the symmetry of BiFeO3 via the oxygen octahedron distortion and proper tilting it is possible to induce the spontaneous polarization from B-site Fe ions and a partial reduction of Fe3+ into Fe2+ results in ferromagnetic super-exchange Fe3+−O−Fe2+ interactions, providing room temperature multiferroics that have the same origin for both ferroelectricity and ferromagnetism. The dynamic room-temperature ME effect which originates from the intrinsic ME interaction between magnetic moments and ferroelectric polarization is evidenced by the resonant behavior of the complex dielectric permittivity and complex magnetic permeability at microwaves. A striking interplay between ferroelectricity and magnetism is demonstrated by the electric polarization reversal and magnetization reversal, both actuated by applied magnetic and electric fields. The room-temperature multiferroic material combines the advantages of type I multiferroics and type II multiferroics, thus providing great potential for construction of low-energy nonvolatile magnetoelectric storages and sensors.