Effect of cobalt substitution on structural, impedance, ferroelectric and magnetic properties of multiferroic Bi2Fe4O9 ceramics

Abstract

Structural, impedance, ferroelectric and magnetic properties were examined in multiferroic Bi2Fe4(1?x)Co4xO9 (0?x?0.02) ceramics synthesized via solid-state reaction method. X-ray diffraction analysis and Rietveld refinement showed secondary phase formation (for x?0.01) which was subsequently confirmed from room temperature Raman spectroscopy study. The frequency dependence of impedance and electric modulus of the material showed the presence of non-Debye type relaxation in all the samples. The values of the activation energies calculated from imaginary impedance and modulus lay in the range of 0.92�0.99�eV which confirmed that the oxygen vacancies play an important role in the conduction mechanism. Moreover, suitable amount of Co substitution significantly enhanced the remnant polarization (2Pr) from 0.1193�?C/cm2 (x=0) to 0.2776�?C/cm2 (x=0.02). Besides, room temperature M-H measurement showed improved ferromagnetic hysteresis loop for all the modified samples. The remnant magnetization (Mr) and coercive field (Hc) increased from 0.0007�emu/gm and 42�Oe for x=0�0.1401�emu/gm and 296�Oe for x=0.02. The improved ferroelectricity was due to Co 3d-O 2p hybridization and enhanced magnetization originated from the partial substitution of Co3+ ions leading to breakdown of balance between the anti-parallel sub lattice magnetization of Fe3+ ions. � 2016 Elsevier Ltd and Techna Group S.r.l.