Large magnetocapacitance in electronic ferroelectric manganite systems

We have observed a sizable positive magnetocapacitance (similar to 5%-90%) in perovskite Pr0.55Ca0.45MnO3 and bilayer Pr(Sr0.1Ca0.9)(2)Mn2O7 system under 5 T magnetic field across 20-100 K below the magnetic transition point T-N. The magnetodielectric effect, on the other hand, exhibits a crossover: (a) from positive to negative for the perovskite system and (b) from negative to positive for the bilayer system over the same temperature range. The bilayer Pr(Sr0.1Ca0.9) 2Mn2O7 system exhibits a sizable anisotropy as well. We have also noticed the influence of magnetic field on the dielectric relaxation characteristics of these systems. These systems belong to a class of improper ferroelectrics and are expected to exhibit charge/orbital order driven ferroelectric polarization below the transition point T-CO. Large magnetocapacitance in these systems shows a typical multiferroic behavior even though the ferroelectric polarization is small in comparison to that of other ferroelectrics. (C) 2013 AIP Publishing LLC