Strain tuned collinear-Magnetism in Mn and Co based rare-earth oxide heterostructures

Most research on rare-earth (RE)/transition-metal (TM) oxides focuses on the orthorhombic phase, but there exists a hexagonal phase, h-RETMO₃, with unique magnetic and magnetoelectric properties. However, magnetic frustration due to a triangular lattice leads to spin canting and weak-ferromagnetism (wFM). Previous reports show that the magnetism of these systems can be tuned by inducing in-equivalent magnetic sublattices to reduce the magnetic frustration. Here we report theoretical investigations of heterostructures of different Mn- and Co-based h-RETMO₃s. REMnO₃ oxides are well known for their double exchange interactions and mixed oxidation states. Thus, it is possible to create inequivalent magnetic sublattices in Mn-based h-RETMO₃s. Initial results show that if we force the system into a collinear AFM configuration, one of the three Mn (Co) in the triangular lattice of h-LuMnO₃ (h-LuCoO₃) goes into a low spin state (changes its oxidation state) to reduce frustration. These spin and oxidation states can be tuned by modifying the octahedral environment, e.g., by strain in heterostructures and superlattices.