Abstract
In this paper, we investigated the structural, magnetic, and dielectric properties of the compounds La-0.65 Bi(0.05)Sr(0.3)Mn(1-x)GaxO(3) (x = 0 and 0.06) synthesized with the ceramic method. The structural studies of the compounds showed their indexation in the rhombohedral structure with the R-3C space group. The M(T) investigations under an applied magnetic field of 0.05 T presented a single ferromagnetic-paramagnetic phase transition around the Curie temperature T-C. Gallium doping with non-magnetic coupling between Ga3+-O2--Ga3+ reduces the Curie temperature to lower values: T-C = 360 K for x = 0 and T-C = 350 K for x = 0.06. The impedance plot at room temperature (T = 330 K) appeared as uncompleted semicircular arcs off-centered on the real axis, indicating that the electrical conduction arises from the grain boundaries. The electrical equivalent circuit has been proposed as a parallel combination of grain boundary resistance R-gb and constant phase element impedance (Z(CPE)) to explain the impedance results. The study of the conductivity with respect to frequency at T = 303 K displayed the reduction of the electron hopping (coulombic interactions) with gallium doping.