Electrical, thermal and magnetic properties of Bi doped La_0.7−xBi_xSr_0.3MnO₃ manganites

Highlights: • The Bi-doped compounds follow small polaron hopping model in high temperature range. • There are evidences about existence of magnetic polarons. • Magneto-resistance of these compounds increase with Bi-doping. • High temperature thermoelectric power data follows SPH model. - Abstract: We report detailed electrical, magnetic and thermoelectric studies on Bi-doped L_0.7−xBi_xSr_0.3MnO₃ (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