Anomalous ferromagnetism in spray pyrolysis deposited multiferroic BiFeO3 films

Oriented polycrystalline BiFeO3 (BFO) films are deposited on single crystal LaAlO3 (001) substrates by nebulized spray pyrolysis technique at low temperature of similar to 300 degrees C. Annealing of the as deposited films in air and oxygen at similar to 550 degrees C for 1 h is found to produce crystallization and BFO phase formation. X-ray diffraction results show rhombohedral disordered perovskite structure with space group R3m. As revealed by atomic force microscopy, grain size increases with oxygen annealing. Magnetic measurements show well-defined hysteretic loops at room temperature for both the films. However, oxygenation leads to dramatic increase in room temperature ferromagnetism as evidenced by large saturation magnetization of similar to 250 emu/cm(3). This enhanced magnetization is attributed to the presence of iron oxide rich nanoclusters due to oxygen annealing. (c) 2007 American Institute of Physics.