Effects of oxygen content on the electric and magnetic properties of BiFeO3 compound

Abstract Multiferroic BiFeO δ ( δ =2.67, 2.95 and 3.02) compound of various oxygen contents ( δ ) have been prepared by gel sol method. The influence of oxygen contents on the structure, electric and magnetic properties of BiFeO 3 compound has been investigated. X-ray diffraction (XRD) measurements indicate that all the samples of BiFeO δ have the same crystal structure regardless of oxygen content. The SEM micrograph reveals microstructures comprising of grains with various sizes from 200 nm to 1 µm. XPS study confirms the coexistence of Fe 3+ and Fe 2+ ions in BiFeO δ compound. The M ( H ) curves exhibit weak ferromagnetic behavior with unsaturated magnetization at room temperature, independent of the oxygen content. The M ( T ) curves of suggest anti-ferromagnetic behavior with Neel temperature of ~370 °C for BiFeO 2.95 and BiFeO 3.02 samples and paramagnetic behavior of BiFeO 2.67 sample from RT up to 500 °C. The experimental results show that the antiferromagnetic ordering is strongly correlated with the oxygen content and is almost entirely suppressed in BiFeO δ with δ =2.67. The effect of oxygen vacancies is to weaken the magnetic ordering rather than to enhance it as previously suggested in the literature.