Influence of multi-ion co-doping and NiFe₂O₄ layer on the properties of BiFeO₃/NiFe₂O₄ composite films by sol-gel

Pure BiFeO₃ (BFO), BiFeO₃/NiFe₂O₄ (BFO/NFO) and multi-ion co-doped Bi_0.89Sm_0.11Fe_0.94Mn_0.04Cr_0.02O₃/NiFe₂O₄ (BSFMC/NFO) thin films have been synthesized by using a sol-gel method. The influences of multi-ion co-doping and NFO layer co-doping on its crystalline structural, leakage current and multiferroic properties are investigated. The results indicate that an asymmetry of J-E curves at negative and positive applied electric fields is clearly observed in the BFO/NFO and BSFMC/NFO films, which is apparently related to the effects of the interface between the BFO and NFO layers. Moreover, improved ferroelectric and ferromagnetic properties are observed in the BSFMC/NFO film simultaneously, e.g. large remanent polarization and saturation magnetization is 66.18 μC/cm² and 34.20 emu/cm³, respectively.