Structural, magnetic and magnetotransport properties of La0.67Ba0.332−xRbxMnO3 perovskites prepared by flux method

We have undertaken a systematic study of the effect of Rb+ doping on the X-ray diffraction, magnetic and electric transport properties of the mixed valence perovskites La0.67Ba0.33−xRbxMnO3 (0≤x≤0.1), prepared by the flux technique. X-ray diffraction and structure refinement showed the formation of single-phase compositions with rhombohedral symmetry with R3¯c space group. Magnetization measurements in a magnetic field of 0.05 T confirm a transition from ferromagnetic (FM) to paramagnetic (PM) phase with increasing temperature. The Curie temperature TC decreases from 340 K (x = 0) to 296 K (x = 0.1). The decrease of Tc can be explained by the Mn4+ content increase. Upon Rb doping, the temperature TM-Sc decreases, in accordance with the evolution of TC values (from 340 to 296 K). The electrical resistivity concluded that the metallic part (below TM-Sc) can be explained by the following equation ρ(T)=ρ0+ρ2T2+ρ4.5T4.5, signifying the importance of the domain boundary / grain, combination of electron-magnon, electron-electron and electron phonon scattering processes. At higher temperature (T > TM-Sc) the semiconducting regime, the adiabatic small polarons hopping mechanism (ASPH) was found to fit well.