Effect of Gd-doping on magnetic, ferroelectric, and optical properties of BiFeO3 multiferroic nanoparticles synthesized by Sol-gel route

Multiferroic nnanoparticles (NPs) of pristine BiFeO3 (BFO) and Gd-doped BFO, Bi1 - xGdxFeO3 (x = 0.01, 0.03, and 0.05) were synthesized by ethylene glycol-based sol-gel route. The impact of Gd-concentration on their structural, optical, ferroelectric, and magnetic characteristics has been examined. XRD confirmed the phase purity and, it was found that the rhombohedral distorted perovskite structure remained the same on Gd-doping. The average particle size, as determined by FE-SEM, decreased exponentially in the following manner, 46 -> 44 -> 42 -> 41 nm for Gd-doping level varying as 0% -> 1% -> 3% -> 5%, respectively. In Raman spectra of 5%-Gd-doped NPs, the phonon modes corresponding to A1 - 3, A1 - 4 and E peaks show a red shift of 2.6 cm- 1, 2.5 cm- 1, and 5.2 cm- 1, respectively. Well-defined absorption peak at 459 nm was seen in UV-visible absorption spectra of BFO NPs which blue-shifted to 446 nm and the bandgap varied linearly with dopant concentration. 3% Gd-doping was found to be optimum as it caused more than 100% enhancement of the saturation and remanent magnetization, upto 0.702 emu/g and 0.057 emu/g, respectively. In ferroelectric measurements, all samples showed non-saturating P-E hysteresis curves, with pristine BFO having the maximum remnant polarization. These Gd-doped BFO NPs with enhanced magnetic and optical properties are well-suited for applications in photocatalysis and spintronics.