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

Abstract We have investigated the role of the grain bound-ary on the resistive magnetodielectric property of polycrys-talline γ-Fe2O3 through impedance spectroscopy measure-ments. Depending on the sample preparation temperature, the dielectric constant of γ-Fe2O3 is significantly different especially at low frequencies (<104 Hz) and high temper-atures (>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 mag-netoresistance. Through the experimentally obtained resis-tance ratio between the grain and the grain boundary, we can reproduce the magnetodielectric curves based on the Maxwell–Wagner model and the measured magnetoresis-tance. PACS 75.50.Gg · 75.80.+q · 77.22.Ch