Effects of Nd3+ and high-valence Nb5+ co-doping on the structural, dielectric and magnetic properties of BiFeO3 multiferroics

Bi0.90Nd0.10Fe1−xNbxO3 (0 ≤ x ≤ 0.05) multiferroics have been studied to reveal the effect of Nb doping on the physical properties of the neodymium modified BiFeO3. These samples have been synthesized via conventional solid state reaction method. The structural characterization was performed by XRD technique and Rietveld refinement. Rietveld refinement results confirmed that all samples crystallized in rhombohedral symmetry. In the vicinity of anti-ferromagnetic Neel-temperature (TN), an anomaly was observed in dielectric constant (ɛ′) and loss tangent (tan δ) which indicates the existence of magnetoelectric coupling. It is observed that with Nb doping dielectric constant was reduced and Neel temperature shifted towards higher temperature. The impedance (Nyquist plots) and modulus spectroscopy revealed that materials possess non-Debye type of relaxation. The doping of donor ion is able to suppress the existence of oxygen vacancies which results in increase in resistivity. The B-site doping by higher valence ion suppresses the existing modulated spin structure by structural distortion, results in released net magnetization. The room temperature remanent magnetization increased with Nb doping and all powder samples possess weak ferromagnetism. The possible reasons for the notable magnetic and dielectric performance of prepared samples were discussed.