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 unreported G-type d_3z²-r²/0.0pt0exd_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.