Near-interface magnetotransport in La0.75Sr0.25MnO3 epitaxial films on SrTiO3 substrate

Abstract

The magnetotransport properties of La0.75Sr0.25MnO3 (LSMO) films epitaxially grown on SrTiO3 (0 0 1) substrate were studied. The Curie temperature (Tc) of LSMO films decreases from 300 to 105 K with a reduction in the film thickness to 5 nm. A clear metal–insulator transition is observed at a temperature consistent with Tc for films thicker than 10 nm. However, the 5 nm thick film displays an insulative characteristic along with a high magnetoresistence effect in a wide range of temperatures below and above Tc. A phase-separation phenomenon in the 5 nm thick film was demonstrated by thermally activated hopping transport between ferromagnetic metallic domains embedded in an insulative matrix at temperatures below Tc, but between paramagnetic metallic domains at temperatures above Tc. It was also confirmed by conductive atomic force microscopy images.