Magnetodielectric effect and conduction mechanism in BFO-REMO multiferroics

Abstract

We report herein the synthesis and suitable approach to improve the magnetoelectric (ME) coupling of Bismuth ferrite oxide (BFO) by fabrication of BFO_1−x-GMO_x and BFO_1−x-DMO_x solid solutions for 0.0≤ x ≤0.2 by the autocombustion method. The materials have been systematically characterized and examined to study the possibility of the compositional driven structural phase transition and its correlation with the ME coupling. Detail of the structural, microstructural, thermal, dielectric, ferroelectric, magnetic, magneto-dielectric, and magneto-impedance properties will be shown in the light of the bring down of magnetic ordering temperature of BiFeO₃ towards room temperature as a function of increasing GdMnO₃ and DyMnO₃ concentration. The dielectric and electrical properties as a function of the magnetic field indicated the signature of ME coupling in samples with increased GdMnO₃ and DyMnO₃ composition, suggesting an optimization of functional properties of lead-free doped BiFeO₃. In pure BiFeO₃ and all the combinations of BFO_1−x-GMO_x and BFO_1−x-DMO_x was found that the transport mechanism is a Space-Charge-Limited mechanism. We performed our measurements in a temperature range of 100-500K. The Fowler-Northeim Conduction Mechanism fit was used but we found that it does not describe or fit the data. The same happened with Schottky Barrier- and Pool-Frenkel fitting. We determined that the relaxation process occurring in our samples is of the kind of space charge polarization. The charge carrier density and the general density of state decreases with increasing temperature, but not the mobility of the samples, suggesting a hopping mobility type of small polaron.