Double metal-insulator transitions and low-temperature resistivity minimum in La_(1/3)Nd_(1/3)Ba_(1/3)MnO_3 manganite

La_(1/3)Nd_(1/3)Ba_(1/3)MnO_3 polycrystalline bulk samples in single phase form with colossal magnetoresistant effect were synthesized in air atmosphere by the conventional solid phase reaction process for ceramic,and their fundamental magnetoelectronic properties were discussed.X-ray diffraction pattern shows that the manganite substituted with two kinds of rare earth element has a cubic perovskite structure,instead of a rhombohedral.The temperature dependence curve of magnetization reveals the existence of spin ice due to the competition of ferromagnetism and antiferromagnetism in the manganite containing ions of Mn3+ and Mn4+.The melting point of spin ice shifts toward low temperature with the increase of applied field.At H = 40 kOe,the phenomenon of spin freezing disappears.At room temperature,above the Currie temperature(~250 K),the hysterisis loop shows the behavior of parasitic ferromagnetism likely contributed by the fluctuation of lattice distortion.Double metal to insulator transitions,both strongly field dependent,were observed in the temperature dependence curve of resistivity.The resistivity peak near the Currie temperature is oriented from the intrinsic contribution of La1/3Nd1/3Ba1/3MnO3 crystal,while the other peak at ~190 K sensitive to both applied field and sintering time is likely to be related to the tunneling of spin-polarized electrons at grain boundaries.An anomalous minimum of electrical resistivity at ~40 K reveals the existence of local magnetic disorders.By a simulation with the traditional least square method,we believe that the anomalous minimum fits the Kondo theory for diluted magnetic alloy.