Manipulating Interface Magnetism in Manganite Thin Film Membranes by Substrate Surface Chemistry

We demonstrate an unexpected substrate dependence of the magnetic properties of complex oxide thin film membranes. While the tunable magnetism of complex oxides is attractive for many applications, device integration has long been limited by the strict substrate requirements necessary for high-quality film growth. Recently, water-soluble sacrificial layers have been used to separate oxide thin films from the substrate after growth, decoupling the structural and chemical degrees of freedom at the interface. This approach is hoped to enable integration with previously incompatible material platforms, but interface studies of transferred films remain limited. In this work, we use polarized neutron reflectometry and secondary ion mass spectroscopy to provide a detailed understanding of depth-dependent chemistry and magnetization of LaMnO₃ membranes. We find that the final substrate plays a key role in either incorporating or excluding hydrogen species at the surfaces of transferred LaMnO₃ thin films, modifying the magnetism in these interfacial regions. Despite elimination of the epitaxial relationship, the choice of substrate influences the magnetism within the transferred membranes to an unexpected degree, with important implications for integration into existing silicon-based technologies.