Magnetoelectric properties of Mn-substituted BiFeO3 thin films with a TiO2 barrier

Multiferroic thin films with the general formula TiO₂/BiFe_1−xMn_xO₃ (x=0.00, 0.05, 0.10 and 0.15) (TiO₂/BFMO) were synthesized on Au/Ti/SiO₂/Si substrates using a chemical solution deposition (CSD) method assisted with magnetron sputtering. X-ray diffraction analysis shows the thin films contained perovskite structures with random orientations. Compared with BFMO films, the leakage current density of the TiO₂/BFMO thin films was found to be lower by nearly two orders of magnitude, and the remnant polarizations were increased by nearly ten times. The enhanced ferroelectric properties may be attributed to the lower leakage current caused by the introduction of the TiO₂ layer. The J-E characteristics indicated that the main conduction mechanism for the TiO₂/BFMO thin film was trap-free Ohmic conduction over a wide range of electric fields (0-500 kV/cm). In addition, ferromagnetism was observed in the Mn doped BFO thin films at room temperature. The origin of ferromagnetism is related to the competition between distortion of structure and decrease of grain size and decreasing net magnetic moment in films due to Mn doping.