Tuning Magnetism And Crystal Orientations By Octahedral Coupling In Lacoo3/Lamno3 Thin Films

(LaCoO3/LaMnO3)(5) multilayers with fixed LaMnO3 thickness and varying LaCoO3 thickness grown on SrTiO3 (001) substrates are studied by scanning transmission electron microscopy at the atomic scale. Utilizing peak pairs analysis on annular bright field images, the precise atomic positions and the degree of octahedral rotation are obtained. Our study shows that the c axis of LaMnO3 sandwiched by LaCoO3 layers experiences a transition from the in-plane direction to the out-of-plane direction as the LaCoO3 layer thickness increases, due to the oxygen octahedral coupling with LaCoO3 layers. An abnormal suppression in saturation magnetization with increasing the thickness of the LaCoO3 is observed and ascribed to the enhanced MnO6 octahedral rotation. Our work provides a way to tune the magnetic properties of epitaxially grown thin films via interfacial octahedral engineering.