Insights on the role of defects on the magnetic and magneto electric coupling effects in nano BiFeO3

Highlights: • First experimental elucidation of both the weak ferromagnetic ordering and magneto electric coupling in nano BiFeO3. • Magnetic and magneto electric coupling are elucidated by magnetization and P-E loop studies under magnetic field. • Occurrence of weak ferromagnetism is iunderstood in terms of oxygen vacancies as deduced based on Mössbauer results. • Based on the Mössbauer results BiFeO3 nanoparticles are understood to occur in AFM core- weak FM shell configuration. • Results are elucidated in nano BiFeO3 made using citric / tartaric acid leading to observed magneto electric coupling. -- Abstract: BiFeO₃ nanoparticles prepared through sol-gel route using citric acid are studied for their structural, magnetic and magneto-electric coupling effects and are compared with that of calcined BiFeO₃ particles prepared with tartaric acid as the fuel. Nanoparticles of BiFeO₃ prepared with the use of citric acid were observed to be more strongly ferromagnetic and weakly ferroelectric, as compared to that of the bismuth ferrite nanoparticles prepared using tartaric acid as the fuel.Magneto-electric coupling effects were studied in BiFeO₃ prepared by these methods using Raman spectroscopy. These results were further confirmed based on the direct experimental evidence in terms of the variation of polarization with respect to electric field (P-E loop) studies carried out in the nanoparticles of BiFeO₃ under the application of magnetic field.This study brought out new insights on the important role of defects for the observed variations in magnetic and hence magneto-electric coupling effects in BiFeO₃ nano particles prepared using different fuels, as elucidated based on the Mössbauer studies.