Origin of colossal dielectric response in LaFeO3

Polycrystalline LaFeO3 was prepared by the conventional solid-state reactions route. X-ray diffraction was applied to check the phase formation. The Fe57 Mössbauer spectrum collected at room temperature shows the magnetic ordering in the system. Dependence of the magnetization on the applied field (up to 9 T) is characteristic of weak ferromagnetism, induced by canted anti-ferromagnetically coupled spins. When explored in a wide temperature (221-300 K) and frequency (1 Hz-10 MHz) range, AC electrical properties reveal three relaxations. An equivalent circuit model with three RC loops in series is used to extract the electrical parameters associated with these relaxations. The electrical conduction and dipolar relaxation are dominated by polaronic hole hopping between Fe4+ and Fe3+. Analysis of the AC electrical data explores the presence of Maxewell Wagner polarization in the system. Colossal dielectric response in LaFeO3 is extrinsic, and its origin lies in the extended defects at grain-grain interfaces and sample-electrode contacts, whereas the intrinsic static dielectric constant is weakly temperature dependent and lies below 75 in the whole temperature range (221-300 K).