Magnetic properties and impedance spectroscopic analysis in Pr_0.7Ca_0.3Mn_0.95Fe_0.05O₃ perovskite ceramic

The orthorhombic Pr_0.7Ca_0.3Mn_0.95Fe_0.05O₃ manganite is subject to magnetic and impedance spectroscopy measurements. This sample shows a paramagnetic to ferromagnetic phase transition at about 90 K. According to the Banerjee criterion, the nature of the magnetic transition is found to be of second order.The conductance spectra for Pr_0.7Ca_0.3Mn_0.95Fe_0.05O₃ ceramic obey the power law variation for characterizing the hopping dynamics of charge carriers. The activation energies extracted from the dc conductance and hopping frequency show a positive correlation. Using the scaling approach, the conductance spectra are merged into a single master curve, confirming the validity of the time–temperature superposition principle. Equally, a strong deviation from the Summerfield scaling is observed. The random barrier model (RBM) is applied to correct this anomaly and a single master curve is constructed with a positive value of the scaling parameter α. Such parameter indicates a coulomb exchange between the interacting particles. Impedance results confirm the contribution of the resistive grain boundary on the electrical properties and the appearance of multiple electrical relaxation phenomena in Pr_0.7Ca_0.3Mn_0.95Fe_0.05O₃ sample. From the evolution of the derivative ANC with temperature, we confirm the presence of various conduction mechanisms. The Nyquist plots show that the increase in temperature is followed by a decrease in the grain resistance (R_g) and the grain boundary resistance (R_gb) values. Such monotonic decrease confirms a predominant role of grain boundary contribution in governing the transport properties of Pr_0.7Ca_0.3Mn_0.95Fe_0.05O₃ compound.