Evidence of spin-two phonon coupling and improved multiferroic behavior of Bi1−xDyxFeO3 nanoparticles

Rare earth Dy substituted BiFeO3 (Bi1−xDyxFeO3) nanoparticles with x=0.03, 0.05 and 0.10 were prepared by a sol-gel method. Rietveld analysis of the X-ray diffraction patterns and Raman spectroscopy confirmed substitution induced phase transformation from rhombohedral to orthorhombic phase for x=0.10. In Raman spectra, the broad band ranging from 900 to 1400 cm−1, associated with strong spin-two phonon coupling behavior, was observed. Magnetic studies showed enhancement in magnetization in which the saturation magnetization of 5.5 emu/g for x=0.10 sample has been measured. Dielectric measurements showed magnetoelectric coupling around Neel temperature in all the samples. Conductivity of the samples decreases with increasing Dy concentration, indicating suppression of oxygen vacancies. The change in Bi-O and Fe-O bond lengths with increasing Dy content observed from infrared spectroscopy analysis is also found to be in agreement with Rietveld refinement results.