Magnetodielectric effect and conduction mechanism in BFO-REMO multiferroics
Masso Ferret, Roberto
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We report herein the synthesis and suitable approach to improve the magnetoelectric (ME) coupling of Bismuth ferrite oxide (BFO) by fabrication of BFO1−x-GMOx and BFO1−x-DMOx 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 BFO1−x-GMOx and BFO1−x-DMOx 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.