Coupling between oxygen octahedron rotations, Jahn-Teller distortion, magnetic ordering and epitaxial strain in LaMnO3 from first principles

LaMnO3 is known to have rich physics due to coupling among orbital ordering, Jahn-Teller distortions and magnetism. However, less attention has been paid to the role of oxygen octahedron rotations and epitaxial strain. In this talk, we show from first principles calculations that oxygen octahedron rotations induce weak ferromagnetism in \textit{Pbnm} LaMnO3 and that octahedral rotations are cooperatively coupled to the Jahn-Teller distortion.. Furthermore, we predict that compressive epitaxial strain drives bulk $A$-type antiferromagnetic Pbnm insulating phase to a ferromagnetic metallic phase. At the phase boundary between the ferromagnetic-metallic and antiferromagnetic-insulating phases, colossal magneto-resistance is expected.