Thickness- and substrate-dependent magnetotransport properties of lanthanum–strontium manganite films with overstoichiometric manganese content

Abstract

Electrical and magnetoresistive properties of the La0.6Sr0.2Mn1.2O3±δ (LSMO) films deposited on SrTiO3 single-crystalline and Al2O3 polycrystalline substrates by magnetron sputtering have been studied. The aim of the study is to understand the effect of substrate type on the thickness-dependent evolution of magnetotransport properties of the films of lanthanum–strontium manganites with overstoichiometric manganese content. It is shown that the decrease in the LSMO film thickness below 1000 nm causes the reduction of Curie temperature (TC) and magnetoresistance value at 300 K concomitant with the increase in electrical resistivity. At the same time, the dependence of electrical and magnetoresistance parameters on the substrate structure and type becomes stronger. It is found that TC of LSMOSTO films exceeds and resistivity is smaller than the respective parameters of LSMOAO films, and the difference grows with the decrease in the film thickness. All the results show that the behavior of the doped manganite films with overstoichiometric manganese content differs from that characteristic of stoichiometric in manganese films. These observations can be attributed to the effect of manganese excess on the film growth mechanism, making it different from the manganite films of other compositions.