Exploring lattice effects on transport properties in La 0.7Sr0.3MnO3/Al2O3 superlattices

Abstract

Superlattice modulation and interfacial dilatation in manganite/alumina multilayers were used to explore lattice effects on transport behaviour. Epitaxial growth and high quality of stacking as well as structural coherency were confirmed by x-ray measurements. As the measure of lattice distortion, the average lattice spacing, structural coherency length, Curie temperature, magnetization, coercive field Hc as well as resistance are found to be functions of the interface fraction. Accordingly, we divided each manganite layer into two parts, i.e., weakly distorted 'innermost' atomic layers and strongly dilated interfacial atomic layers, as is well clarified by observation of two component magnetization loops and huge variation in resistance measured with current in and perpendicular to plane (i.e. CIP and CPP). The low-resistive innermost part with a 'bulk'-like soft magnetic behaviour functions as a conductance channel for the CIP case, whereas the high-resistive interfacial part rules the CPP data, leading to a low-magnetotunnelling effect at 4.2 K and an enhanced colossal magnetoresistance at the relevant transition temperature. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.