Influence of Y doping on structural, vibrational, optical and magnetic properties of BiFeO3 ceramics prepared by Mechanical Activation

Y substituted BiFeO3 (Bi1−xYxFeO3; x=0.0-0.1) polycrystalline ceramics were synthesized by Mechanical Activation. The effect of varying composition of Y substitution on the structural, vibrational, optical and magnetic properties of doped BiFeO3 (BFO) ceramics has been investigated. Rietveld refinement of X-ray diffraction patterns reveals that all samples crystallize in distorted rhombohedral structure with R3c symmetry and no structural transition has been observed. Raman spectroscopy also confirmed the distorted perovskite structure with R3c space group. Optical studies in the spectral range 1-4.5 eV were dominated by two d-d and three charge transfer (C-T) transitions. The optical band gap decreases from 2.11 to 2.01 eV with increasing Y substitution. Room temperature magnetic measurements showed weak ferromagnetic ordering and enhancement in magnetization with increasing Y concentration. Mechanical activation leads to significantly altered magnetic properties, particularly in higher Y-doping samples. The Mössbauer spectra demonstrate the suppression of spiral spin modulation of the magnetic moments resulting in enhanced ferromagnetism with increasing doping concentration. Significant increase in Néel temperature TN in the substituted compounds was discussed on the basis of structural distortions.