Magnetic and Magneto-Transport Properties of the Sb Doping Mn Site in La0.67Ba0.33Mn1−xSbxO3 (0.03 and 0.07) Manganites

We investigate the effect of Sb5+ doping at Mn-site in La0.67Ba0.33Mn1−xSbxO3 (LBMO-Sbx) on the magnetic and magneto-electrical properties. The variation of the magnetization M versus temperature T, under an applied magnetic field of 0.05 T, reveals a ferromagnetic–paramagnetic transition for all samples. The resistivity and magneto-transport measurements are performed using standard four-probe assembly with and without magnetic fields. The temperature dependence of electrical resistivity shows that all samples undergo a sharp metal–semiconductor (M–SC) transition at a temperature (TM–SC), accompanying the ferromagnetic–paramagnetic transition. The peak resistivity ρmax is noted at the metal–semiconductor transition temperature (TM–SC) and lowering in TM–SC is observed for higher concentrations of Sb5+. The resistivity data have been analyzed in two parts. Firstly, in the metallic region below TM–SC the resistivity data is fitted with three degree polynomial. Secondly, in the semiconducting region above TM–SC data have been fitted with Small Polaron Hopping models. Above all, the magnetoresistance study showed a peak which has a high value around the M–SC transition temperature. The dependence of resistivity on the temperature and magnetic field data is used to deduce the magnetic entropy change.