Low-field magnetoresistance of (1- x )La 0.7 Ca 0.3 MnO 3 + x La 1.5 Sr 0.5 NiO 4 nanocomposite

In this report we present low-field magnetoresistance (LFMR) of (1 − x)La0.7Ca0.3MnO3 + xLa1.5Sr0.5NiO4 (x­ =0–0.3) nanocomposites at temperatures ranging from 30 to 300 K. These materials were synthesized by reactive mechanical ball milling combined with the heat treatment. Experimental results have revealed that the Curie temperature is almost independent of x, while the metal–insulator transition temperature shifts from 254 K for x = 0.0 to 65 K for x = 0.2. Particularly, the samples with x ≥ 0.25 exhibit insulating properties. Magnetoresistance (MR) of all the samples is observed at an applied magnetic field of 3 kOe. In order to explore their MR nature at changing temperature, we analyzed carefully the obtained data basing on the phenomenological model related to the spin polarized transport (SPT) of conduction electrons at grain boundaries.