Strain-induced insulating ferromagnetism in LaMnO3 thin films from first-principles investigations

Abstract Previous experiments have found that LaMnO 3 thin films grown on SrTiO 3 substrate exhibit insulating ferromagnetism different from that of the bulk LaMnO 3 . Utilizing first-principles calculations based on density functional theory, magnetic transitions, energy gaps and spin exchange interactions of LaMnO 3 thin films with different epitaxial strains are investigated, and the effect of the Jahn-Teller distortion, rotation and tilt of oxygen octahedrons on magnetic and electrical properties are analyzed in detail. A relative narrow insulating ferromagnetic area without structural phase transition is obtained during the transition from metallic ferromagnetic phase to insulating A-type antiferromagnetic phase. If the magnetic transition of LaMnO 3 film is attributed to Jahn-Teller distortion, then the metal–insulator transition should be ascribed to the tilt of the oxygen octahedron and large change of the O1-Mn-O2 angle in ab plane, which is helpful to understand the insulating ferromagnetic characters during the preparations of the LaMnO 3 superlattices or heterostructures, also indicates that the insulating ferromagnetic properties of LaMnO 3 films can be tuned by epitaxial strain-controlled oxygen octahedrons distortions.