Influence of Nonmagnetic Oxides on Low-Temperature Resistivity Minima in La2/3Sr1/3MnO3-ZrO2 Matrix Composites

Abstract

The unusual low-temperature resistivity upturn of composites La2/3Sr1/3MnO3 doped with nonmagnetic-insulator oxide ZrO2 is presented in this paper. The depth of the resistance minima was found for all samples below 30 K, and the resistance minima were suppressed under the applied magnetic field. At the same time, it is remarkable that the temperature of the resistivity of the samples and the temperature of the resistance minima (T min) are changed from increasing to decreasing as the applied magnetic field increases continuously. Therefore, there are at least two dominant physical mechanisms in the (1−x)La2/3Sr1/3MnO3-xZrO2 system; the grand boundaries tunneling effect will promote the electrical transport but it will be suppressed by the external magnetic fields; on the other hand, the grand boundaries scattering effect will suppress the electrical transport. We indicate that the grand boundaries tunneling effect was the main factor in low doping, and the grand boundaries scattering effect began to play a leading role in the low-temperature upturn with the increase of nonmagnetic oxides quantity by theoretical analyzing; in the meantime, we also consider that it will improve spin-order of the electrons in the system at low temperature after La2/3Sr1/3MnO3 has been doped with a trace of ZrO2.