RESUMEN
We report the low-temperature resistance upturn in sandwiched structures of La2/3Sr1/3MnO3/ZrO2/La2/3Sr1/3MnO3 and La2/3Sr1/3MnO3/LaMnO3/La2/3Sr1/3MnO3, while it disappeared when the interlayer was replaced by YBa2Cu3O7. The experimental data have been analyzed qualitatively and quantitatively. The results show that the low temperature resistance upturn is mainly due to the quantum correction effects driven by the weak localization and the electron-electron interaction in such a strongly correlated system, and the contribution of each factor varies with grain boundaries. Moreover, the resistance upturns are suppressed by a local magnetic field. These findings will help to further understand the physical mechanism of low-temperature resistance upturn in colossal magnetoresistance manganites. Furthermore, it is also helpful to reveal the intrinsic transport mechanism at the interfaces of semiconductor/ferromagnetism and antiferromagnetism/ferromagnetism.
RESUMEN
Systematic studies of the transport properties of La(0.67)Ca(0.33)Mn(1-x)Fe(x)O3 (x=0-0.3) systems showed that with increasing Fe-doping content x the resistance increases and the insulator-metal transition temperature moves to lower temperature. For small doping content, the transport property satisfies metal transport behavior below the transition temperature, and above the transition temperature it satisfies the small polaron model. This behavior can be explained by Fe3+ doping, which easily forms Fe(3+)-O(2-)-Mn4+ channel, suppressing the double exchange Mn(3+)-O(2-)-Mn4+ channel and enhancing the spin scattering of Mn ions induced by antiferromagnetic clusters of Fe ions.