Evolution of structural and magnetic phases in Nd doped BiFeO3 multiferroics with sintering time

The effect of sintering time on the evolution of structural and magnetic phases has been studied in Bi0.8Nd0.2FeO3 multiferroic. These multiferroics were prepared by normal solid state reaction technique. XRD, NPD and VSM characterizations were performed to explore the structural and magnetic properties and correlation between these. The refinement of the XRD patterns using FullProf program show, mixed phase having rhombohedral (R3c) + orthorhombic (Pnma) symmetry in sample sintered for 1 h. For sample sintered for two hours, crystal structure was found to be mixed phase with rhombohedral (R3c) + orthorhombic (Pbam) symmetry and the sample sintered for three hours, it crystallized in pure orthorhombic (Pbam) symmetry. The octahedral tilting is thus found to be changing systematically with the variation of sintering time. The refinement of the neutron diffractions patterns confirms the XRD results of structural evolution with sintering time. The magnetic moment undergoes change in the direction of their preferential alignment from c-axis to along a-axis in the 3 h sintered sample. The M-H loops shows significant enhancement in magnetization from 0.17455 emu/g to 0.35872 emu/g with increase in sintering time from 1 to 3 h. The enhancement in the magnetization is attributed to increase in the canting angle between magnetic spins. Also, the observation of exchange bias effect with discontinuous variation in exchange bias field indicates the presence of magnetic anisotropy. The magnetic moments obtained through the magnetic refinement of NPD patterns are found to decrease from 4.6 μB to 3.8 μB with increase in sintering time from 1 to 3 h.