Investigation of structural, magnetic and optical properties of rare earth substituted bismuth ferrite

Polycrystalline BiFeO₃ and rare earth substituted Bi_0.9R_0.1FeO₃ (BRFO, R=Y, Ho and Er) compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds stabilized in rhombohedral structure (R3c space group) and a small orthorhombic phase fraction was observed in BRFO compounds. From the Raman spectra results, the changes in the phonon frequencies (A₁) and line widths suggested lattice distortion in the BRFO compounds as was evidenced in the XRD analysis. Compared to the linear variation of magnetization with magnetic field (M-H) shown by BFO, an obvious M-H loop was observed in BRFO compounds which could be due to the suppression of space modulated spin structure and was explained on the basis of weak ferromagnetism and field induced spin reorientation. UV-Vis spectroscopy evidenced a change in local FeO₆ environment due to shift in the ⁶A_1g→⁴T_2g energy transition band. BRFO compounds with improved remnant magnetization and coercive field are applicable for magnetoelectric devices.