Abstract
We investigated the effect of iron substitutions upon the structural, magnetic, electric, and dielectric properties in Pr0.7Ca0.3Mn1-xFexO3 mixed-valence manganite. The samples were synthesized using the solid-state reaction method and were analyzed by X-ray diffraction, magnetic and impedance spectroscopy measurements. X-ray diffraction analysis shows that all samples were found to be single phase and crystallize in the orthorhombic structure with Pnma space group. While the parent compound Pr0.7Ca0.3MnO3 exhibits a charge order sate, the substituted samples with low amount of iron exhibit a paramagnetic to ferromagnetic transition. However, the Curie temperature T-C decreases with Fe content when we move from x=0.02 to x=0.1. From DC-conductance measurements, a typical semi-conducting behavior without any transition is observed for all investigated samples. Beyond a certain critical temperature noticed T-sat, the DC-conductance begins to saturate and reaches a maximum value. Then, the saturation temperature increases with increasing Fe content to attain T-sat=260 K for x=0.10. The correlated barrier hopping model was used to explain the frequency dependence of AC conductance. Impedance measurements confirm the contribution of the resistive grain boundary on the conduction mechanism. Then, it proves the existence of multiple electrical relaxation phenomena in the studied samples. The dielectric constant is found to be temperature dependent indicating that the compounds are polar dielectrics where the dipole orientation is governed by increasing temperature.