Correlation between epitaxial strain and magnetic properties in La 0.7 Sr 0.3 CoO 3 /La 0.7 Sr 0.3 MnO 3 bilayers

Abstract

Magnetic properties arising at interfaces of perovskite oxides such as La 0.7 Sr 0.3 CoO 3 (LSCO) and La 0.7 Sr 0.3 MnO 3 (LSMO) depend sensitively on the fine details of their structural properties. In this work, we use high-resolution transmission electron microscopy and spectroscopy to examine the structural and electronic phenomena at the interfaces in two LSCO/LSMO bilayers with reversed growth order. Two different strain mechanisms are at work in these films: compressive or tensile epitaxial strain, and distortion of the octahedral tilt pattern to maintain a network of corner-sharing octahedra. While the epitaxial strain is constant regardless of the growth order, the modification of the octahedral tilt pattern depends on whether the film is grown directly on the substrate or as the second sublayer. As a consequence, exchange spring behavior is observed only when the LSCO sublayer is grown first. The different mechanisms of strain accommodation within the oxygen octahedra network in each material proved to be of critical importance in determining the interfacial structure and thus magnetic and electronic properties of the bilayers.