Bismuth Ferrite Thin Films Studied by X-ray Diffraction and Mössbauer Spectroscopy

Bismuth ferrite (BiFeO3, BFO) thin films were deposited on Si/SiO2 substrates with a Pt buffer layer using magnetron sputtering and subsequently annealed under different conditions. The influence of thermal treatment on the structural and magnetic properties was investigated using X-ray diffraction and 57Fe conversion electron Mössbauer spectroscopy. X-ray diffraction results show that as-deposited films are amorphous, while annealing at 550°C initiates crystallization, and further treatment at 600°C leads to the formation of the rhombohedral R3c phase. The broad diffraction peaks indicate the nanocrystalline character of the BFO films. The Mössbauer spectrum of the 100 nm thick film annealed at 550°C exhibits two magnetic sextets with hyperfine fields of approximately 49 T, characteristic of Fe3+ ions in magnetically ordered BiFeO3. Comparison with a powder BFO sample reveals very similar hyperfine interaction parameters, indicating that the local environment of iron ions and the magnetic ordering are largely preserved in the 100 nm thick film.