The effect of artificial grain boundaries on magneto-transport properties of charge ordered-ferromagnetic nanocomposites

Abstract

Nanocomposites of charge ordered insulating Pr_0.67Ca_0.33MnO₃ (PCMO) and ferromagnetic metallic La_0.67Sr_0.33MnO₃ (LSMO) nanoparticles have been prepared by chemical synthesis. Transport and magneto-transport properties of nanocrystalline LSMO and the PCMO–LSMO nanocomposites have been studied in detail. At a low temperature region, upturn of resistivity for both the compounds was observed. The upturn of resistivity is strongly influenced by the external magnetic field. The results are analyzed considering intergranular spin polarized tunneling model. Our study reveals that spin polarized tunneling (SPT) is the dominant mechanism leading to the rise in resistivity especially below T = 60 K. It also indicates that SPT through the grain boundary is significantly modified in nanocomposite compounds, which leads to the enhancement of magnetoresistance and low field magnetoconductance compared to LSMO nanoparticles.