Study of magnetoresistance in nanostructured La2/3Sr1/3MnO3 powder compacts

The magnetotransport properties in nanostructured La2/3Sr1/3MnO3 powder compacts prepared under different pressure (0.4-4 GPa) have been examined. For all samples, high field magnetoresistance (HFMR) effect weakens at T>130K, and there exists Coulomb blockade at T<60K. An increase in the preparation pressure results in systematic changes in the various features. These include a decrease in grain size, a reduction in low-field magnetoresistance (LFMR) within the whole experimental temperature, an enhancement of HFMR at T<200K, and a decrease of HFMR at T>200K. The surface phase and the link condition in grain boundaries are suggested to be responsible for the present observations.