Investigation of cationic disorder effects on the transport and magnetic properties of perovskite Pr_0.7-xRE_xSr_0.3MnO₃ (x=0.0,0.2; RE = Nd, Sm, & Gd)

The strong influence of the A-site cationic size mismatch on the electrical, thermal and magnetotransport properties of Pr_0.7-xRE_xSr_0.3MnO₃ (x=0.0,0.2; RE = Nd, Sm & Gd) pervoskite compound has been reported here. The considerable shifting of the insulator to metal transition temperature (T_IM) with the partial substitution of Pr³⁺ ions by smaller radii rare-earth ions is discussed. The relevance of electron-electron scattering and the application of an adiabatic small polaron hopping (ASPH) model is explained to analyze electrical data. The temperature dependent volume fraction of the metallic ferromagnetic phase obtained from the percolation model of the electrical resistivity demonstrated a well resemblance with magnetic data. Analysis of Thermoelectric Power (TEP) data reveals that electron-magnon scattering is responsible for the thermoelectric transport in the metallic region whereas high temperature insulating region above T_p is well explained by the non-adiabatic SPH model.