Intrinsic insulating ferromagnetism in manganese oxide thin films

By combining genetic algorithm optimizations, first-principles calculations and the double-exchange model studies, we have revealed that the exotic insulating ferromagnetism in LaMnO3 thin film originates from the previously unreportedG-type d(3z2-r2)/d(x2-y2) orbital ordering. An insulating gap opens as a result of both the orbital ordering and the strong electron-phonon coupling. Therefore, there exist two strain-induced phase transitions in the LaMnO3 thin film, from the insulating A-type antiferromagnetic phase to the insulating ferromagnetic phase and then to the metallic ferromagnetic phase. These phase transitions may be exploited in tunneling magnetoresistance-and tunneling electroresistance-related devices.