Structure, leakage mechanism and multiferroic properties of (Mn, Cr) co-doped BiFe0.93Mn0.04Cr0.03O3/NiFe2O4 bilayer film by sol–gel

•(Mn, Cr) co-doped BFMC/NFO bilayer film was synthesized by a sol–gel method.•Structure, leakage current, ferroelectricity and magnetism of the film was studied.•The ferroelectric and ferromagnetic properties was greatly improved simultaneously.•The leakage current mechanism of the BFMC/NFO bilayer film films was analyzed.

(Mn, Cr) co-doped BiFe0.93Mn0.04Cr0.03O3/NiFe2O4 (BFMC/NFO) bilayer film has been prepared on FTO/Glass substrate via a sol–gel method. Enhanced ferroelectric and ferromagnetic properties were obtained in the (Mn, Cr) co-doped BFMC/NFO bilayer film, e.g., large remnant polarization value (Pr = 55 μC/cm2) and large saturation magnetization (Ms = 27.04 emu/cm3). Rietveld refinement of X-ray diffraction data of the bilayer film showed that the BFMC layer was conformed to a BiFeO3 phase with tetragonal lattice type with P4 space group, and NFO layer was a NiFe2O4 phase with cubic lattice type with Fd-3m: 1 space group. The tetragonal phase is in favor of enhanced ferroelectric properties in the BFMC/NFO bilayer film. Moreover, leakage mechanism of the BFMC/NFO bilayer film was also investigated.