Annealing temperature effect on ferroelectric and magnetic properties in Mn-added polycrystalline BiFeO₃ films

We fabricated 5 at.% Mn-added polycrystalline BiFeO₃ films and investigated the annealing temperature effect on structural, ferroelectric and magnetic properties. In the x-ray diffraction patterns, only the diffraction peaks due to the BiFeO₃ structure were observed and no secondary phase could be observed at annealing temperatures between 773 and 923 K. Adding Mn suppressed the leakage current density in the high electric field region when compared to pure BiFeO₃ films. The conduction mechanism of the Mn-added BiFeO₃ films was dominated by Ohmic conduction. Remanent polarization of the Mn-added polycrystalline BiFeO₃ films for an applied electric field of approximately 1.5 mV/cm was 63 μC/cm² for the specimen annealed at 773 K and 46 μC/cm² for the specimen annealed at 923 K, although the remanent polarization still exhibited a tendency to increase with an increase in the electric field. Spontaneous magnetization was obtained at high annealing specimens. This study revealed that the annealing temperature strongly affected the ferroelectric and magnetic properties in Mn-added polycrystalline BiFeO₃ films. In addition, by optimizing the annealing temperature, we realized multiferroics coexistent with spontaneous magnetization and spontaneous polarization at room temperature in the Mn-added polycrystalline BiFeO₃ film.