Effect of grain boundary on resistive magnetodielectric property of polycrystalline γ-Fe2O3

We have investigated the role of the grain boundary on the resistive magnetodielectric property of polycrystalline γ-Fe2O3 through impedance spectroscopy measurements. Depending on the sample preparation temperature, the dielectric constant of γ-Fe2O3 is significantly different especially at low frequencies ( 200 K). The value of the magnetodielectric effect at a specific frequency and the resonance frequency for the maximized magnetodielectric effect are different, although polycrystalline γ-Fe2O3 samples show a quite similar magnetoresistance. Through the experimentally obtained resistance ratio between the grain and the grain boundary, we can reproduce the magnetodielectric curves based on the Maxwell–Wagner model and the measured magnetoresistance.