Microstructural, optical and magnetic characterizations of BiFeO3 multiferroic nanoparticles synthesized via a sol-gel process

Synthesis of high-purity BiFeO3 (BFO) nanoparticles is a very challenging task for the scientific community because small amounts of nonstoichiometric BixFeyOz species usually appear as byproducts in most of the synthesis routes. Here, we report on the synthesis of high-purity BFO nanoparticles via a sol-gel process. XRD, Raman and IR spectra demonstrate that the BFO nanoparticles crystallize in a distorted rhombohedral perovskite structure with a space group of R3c. TEM images reveal that the sizes of the BFO nanoparticles are distributed in the range of 30-200 nm. The UV-Vis absorption spectra display that the bandgap of the BFO nanoparticles is 2.21 eV. Magnetic hysteresis loops show that the BFO nanoparticles exhibit weak ferromagnetic behavior at low temperatures, and an exchange bias effect is also observed. Furthermore, an abrupt increase of magnetization with decreasing temperature is observed at ∼10 K in both ZFC and FC measurements.