Tailoring the structural, optical and magnetic properties of BiFeO3 multiferroic nanoparticles by Ba, Cr co-doping

Phase pure BiFeO3 (BFO) and Bi0.98Ba0.02Fe1-xCrxO3 (x = 0.01, 0.02, 0.03, 0.04) nanoparticles were synthesized by a facile sol-gel route. X-ray diffraction data confirms rhombohedral R3c phase of BFO and Ba, Cr co-doped BFO nanoparticles with a slight distortion at higher dopant concentration. TEM images verified the higher crystallinity of the samples with a significant reduction in particle size (similar to 40 nm) with increasing Cr concentration. The band gap of pristine BFO nanoparticles was found to be 1.8 eV which increases remarkably to a maximum of 2.32 eV for Ba, Cr co-doped BFO nanoparticles. Fe-57 Mossbauer spectroscopy confirmed that no mixed valance state of Fe was present in the Ba, Cr co-doped BFO nanoparticles. Hysteresis loops of all the samples revealed the weak ferromagnetic nature of the co-doped BFO nanoparticles. It was observed that the saturation magnetization increased by more than 3 times when Cr content was increased from 1% to 4%.