Investigation on structural, magnetic and optical properties of Sm-Co co-substituted BiFeO${}_3$ samples

Sol-gel derived Sm-Co co-substituted BiFeO${}_3$ ceramics (Bi${}_{1-x}$SmFe${}_{1-x}$Co${}_x$O${}_3$ with x = 0.0, 0.01, 0.02 and 0.03; named as BFO, BSFCO-1, BSFCO-2 and BSFCO-3, respectively) were investigated for structural, vibrational, magnetic and optical properties. Distorted perovskite rhombohedral structure with R3c crystal symmetry has been established in X-ray diffraction (XRD) patterns analysis by Rietveld refinement and detailed structural parameters like lattice constants, unit cell volume, bond angles, bond length etc. have been evaluated. Raman spectra further confirmed typical rhombohedral structure of BiFeO${}_3$ by exhibiting 13 clear Raman active phonon (9E + 4A) modes along with second order modes in the wave number range 50-1500 cm${}^{-1}$. Fourier Transform Infrared (FTIR) spectra showed the presence of Fe-O and Bi-O bands and the calculated Fe-O bond length was in good agreement with that obtained from Rietveld analysis. Room temperature magnetization versus magnetic field (M-H) measurement using Vibrating Sample Magnetometer (VSM) showed enhancement of ferromagnetic ordering parameters with increasing Sm-Co content in BiFeO${}_3$ samples. The maximum magnetization values increased from 0.237 emu g${}^{-1}$ for BFO sample to 1.167 emu g${}^{-1}$ for BSFCO-3 sample along with increase in remnant magnetization values. The optical property of Bi${}_{1-x}$SmFe${}_{1-x}$Co${}_x$O${}_3$ samples was investigated by estimating the energy band gap using UV-Visible spectroscopy. The calculated values of energy band gap were varied in the range 2.46 eV-1.81 eV indicating tuning of energy band gap with Sm-Co co-substitution in BiFeO${}_3$ sample.