Electrical transport properties driven by magnetic competition in hole-doped perovskite Pr_1-xBa_xMnO₃ (0.25 x 0.36)

In this work, polycrystalline Pr1-xBaxMnO3 (0.25 <= x <= 0.36) ceramics were synthesized, and their magnetic and electrical transport properties were systematically studied. All samples show two metal-insulator transitions (MITs) corresponding to the high temperature T-MI1 and low temperature T-MI2, respectively, besides the non Griffith phase above the ferromagnetic (FM) transition temperature T-C. Combining the results of the transport and magnetic properties, it is found that the FM transition temperature T-C coincides with the temperature T-MI1, which is linearly related to the A-site ionic radius mismatch variance sigma(2), indicating the enhancement of FM interactions due to the increase of the degree of B-site ordering of Mn3+/Mn4+ ions. The positive correlation between ferromagnetic insulators (FMI) and magnetic interactions, including the FM and short-range antiferromagnetic (AFM) interactions, is confirmed. It is suggested that the first MIT at T-MI1 is attributed to the Mn3+/Mn4+ double exchange interactions and the second MIT at T-MI2 is closely related to the suppression of the AFM interactions under the internal FM field induced by the Mn3+/Mn4+ DE interactions. This work provides not only a theoretical understanding on the origin of MIT at low temperature, but also a new way for adjusting the FMI in perovskite manganese oxide Pr1-xBaxMnO3 for application.