Temperature and Frequency Dependent Electrical Behaviour of Rare-Earth Orthoferrites (RFeO3, R = Nd,Gd)

The electrical properties of the sample RFeO₃ (R = Nd,Gd) were investigated by the study of complex impedance, electric modulus, conductivity, and density of states synthesized through the conventional solid-state reaction technique. The orthorhombic crystal structure was confirmed. The electrical conductivity of RFeO₃ is found to be low at lower frequencies due to space charge polarization and increased gradually, indicating the presence of local charge carriers. The complex impedance study reveals the presence of grain and grain boundary contributions, which are modeled using (RQC) and a combination of (RQC) (RC) electrical circuits. At low temperatures, the grain effect was explained by the quantum tunneling (QTM) model for NdFeO₃ and the correlated barrier hopping (CBH) model for GdFeO₃. At high temperatures, the grain boundary effect was explained by the CBH model for NdFeO₃ and the Non-overlapping small polaron tunneling (NSPT) model for GdFeO₃. The shifting of the peaks (imaginary part of the electric modulus) towards the higher frequency with the increase of temperature was explained by the heat-activated mobile ions speeding up the relaxation process.