Quantum anomalous Hall phase and half-metallic phase in ferromagnetic (111) bilayers of 4d and 5d transition metal perovskites

Extraordinary electronic phases can form in artificial oxide heterostructures, which will provide a fertile ground for new physics and also give rise to novel device functions. Based on a systematic first-principles density functional theory study of the magnetic and electronic properties of the (111) superlattices (ABO(3))(2)/(AB ' O-3)(10) of 4d and 5d transition metal perovskite (B = Ru, Rh, Ag, Re, Os, Ir, Au; AB ' O-3 = LaAlO3, SrTiO3), we demonstrate that due to quantum confinement, bilayers (LaBO3)(2) (B = Ru, Re, Os) and (SrBO3)(2) (B = Rh, Os, Ir) are ferromagnetic with ordering temperatures up to room temperature. In particular, bilayer (LaOsO3)(2) is an exotic spin-polarized quantum anomalous Hall insulator, while the other ferromagnetic bilayers are metallic with large Hall conductances comparable to the conductance quantum. Furthermore, bilayers (LaRuO3)(2) and (SrRhO3)(2) are half metallic, while the bilayer (SrIrO3)(2) exhibits a peculiar colossal magnetic anisotropy. Our findings thus show that 4d and 5d metal perovskite (111) bilayers are a class of quasi-two-dimensional materials for exploring exotic quantum phases and also for advanced applications such as low-power nanoelectronics and oxide spintronics.