Study of ac susceptibility and magneto-resistivity in Ba1−xLaxMnO3 (x = 0.30–0.70) compounds

Ba1−xLaxMnO3 compounds for x = 0.30–0.70 have been prepared in single phase form. Structural transition from orthorhombic symmetry to rhombohedral symmetry has been observed with increase in doping. ac Susceptibility measurements show that all the above materials exhibit paramagnetic to ferromagnetic transitions. Metal–insulator transitions have been observed in electron doped as well as hole doped materials, and the transition temperatures vary from 243 to 340 K. Reentrant semiconducting behaviour is observed in the vicinity of charge ordering temperature in x = 0.50 sample. The colossal magneto-resistivity values are mostly found to increase with decrease in temperature. The correlation between ac susceptibility and electrical resistivity results has been discussed. The low temperature metallic behaviour could be explained only by the electron–electron scattering mechanism in both electron and hole doped materials.