Substitution-driven enhanced magnetic and ferroelectric properties of BiFeO3 nanoparticles

Multiferroic BiFeO3 (BFO) nanoparticles along with co-substitution of Gd, a rare-earth element, and Co, a transition metal, were synthesized through modified Pechini sol-gel process. A compositional-driven structural change in the rhombohedral phase (R3c) due to the inclusion of Gd and Co was identified with the help of X-ray diffraction analysis. Dense oblate nanospheres with average grain sizes less than the spin periodicity of BFO were observed through field emission scanning electron microscopy studies, where the grain sizes were found to decrease with increasing concentration of substituent ions. The co-substitution modified the BFO's original magnetic structure, which eventually led to the enhancement of spontaneous magnetization as evident from their M - H hysteresis loops. Large difference between ZFC and FC curves indicates some glassiness in the co-substituted samples. In addition to the observed distortion in crystal structure, a considerable reduction of Fe2+ ions confirmed by XPS has favored enhancement of polarization. (C) 2015 Elsevier B.V. All rights reserved.