Electrical, thermal and magnetic properties of Bi doped La _0.7-xBi_xSr_0.3MnO₃ manganites

We report detailed electrical, magnetic and thermoelectric studies on Bi-doped L_0.7-xBi_xSr_0.3MnO ₃ (0 ≤ x ≤ 0.25) manganites. The XRD patterns and Rietveld analysis show that the studied materials are single phased. All the compounds, exhibit the expected metal-insulator transition and a decrease in the characteristic metal-insulator transition temperature (T_MI) is observed to decrease with increase in Bi-content. Low temperature resistivity data indicates that grain boundaries and electron-electron scattering processes contribute vital role in the conduction process. Magnetic studies also show that the Curie temperature T_C is found to decrease with Bi-content. It is observed that M_ZFC and M_FC curves become more manifested as Bi-content is increased which indicates an increase in magnetic frustration arising due to bending of Mn-O-Mn bond. High temperature analysis on the electrical resistivity and thermoelectric power data indicates that small polaron hopping (SPH) model is valid for all the samples.