Effect of Gd-Ti co-substitution on structural, magnetic and electrical properties of multiferroic BiFeO3

Bi1−xGdxFe1−xTixO3 (x=0.05, 0.10, 0.15 and 0.20) powder was synthesized by a facile sol-gel route and the phase was confirmed by powder X-ray diffraction analysis. Rietveld analysis corroborates the following sequence of phase transitions with increasing concentration of x: rhombohedral (R3c) → orthorhombic (Pbnm) → cubic (Pm3¯m). X-ray photoelectron spectroscopy revealed the fact that Fe exists predominantly as +3 state in the co-substituted sample. Scanning electron micrographs evidences the reduction in particle size with increase in concentration of the co-substituents. Broadening, suppression and shifting of Raman modes with the increase in concentration of Gd and Ti supports the structural phase transition. UV-Vis diffuse reflectance spectra showed a decrease in the energy gap with the increase of the co-substituent concentration. The magnetic behavior of the samples demonstrates the significant increase in latent magnetization with the increase in co-substituent concentration which was substantiated by Arrott-Belov-Kouvel plot. Temperature dependent dielectric analysis of the co-substituted samples showed an anomaly in the vicinity of Neel temperature (TN) indicating a change in the magnetic ordering. The leakage current density is found to be decreased with the increase in concentration of Gd and Ti.