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In this work, we studied time-reversal-breaking topological phases as a result of the interplay between antiferromagnetism and inverted band structures in antiferromagnetic double perovskite transition-metal Sr2FeOsO6 films. By combining the first-principles calculations and analytical models, we demonstrate that the quantum anomalous Hall phase and chiral topological superconducting phase can be realized in this system. We find that to achieve time-reversal-breaking topological phases in antiferromagnetic materials, it is essential to break the combined symmetry of time reversal and inversion, which generally exists in antiferromagnetic structures. As a result, we can utilize an external electric gate voltage to induce the phase transition between topological phases and trivial phases, thus providing an electrically controllable topological platform for future transport experiments. [ABSTRACT FROM AUTHOR]

The electronic and magnetic properties of distorted monoclinic double perovskite Sr2CeIrO6 were examined based on both experiments and first-principles density functional theory calculations. From the calculations we conclude that low-spin-state Ir4+ (5d5) forms a rare weakly antiferromagnetic (AFM) orbital ordered state derived from alternating occupation of slightly mixed egπ symmetry states in the presence of spin-orbit coupling (SOC). This orbital ordering is caused due to the competition between the comparable strength of Jahn-Teller structural distortion and SOC. We found both electron-electron correlation and SOC are required to drive the experimentally observed AFM-insulating ground state. Electronic structure investigation suggests that this material belongs to the intermediate-SOC regime, by comparing our results with the other existing iridates. This single active site double perovskite provides a rare platform with a prototype geometrically frustrated fcc lattice where among the different degrees of freedom (i.e., spin, orbital, and lattice) SOC, structural distortion, and Coulomb correlation energy scales compete and interact with each other. [ABSTRACT FROM AUTHOR]

Using first-principles density-functional theory, we have investigated the electronic and magnetic properties of recently synthesized and characterized 5d double-perovskites Sr2BOsO6(B=Y,In,Sc). The electronic structure calculations show that in all compounds the Os5+ (5d3) site is the only magnetically active one, whereas Y3+, In3+, and Sc3+ remain in nonmagnetic states with Sc/Y and In featuring d0 and d10 electronic configurations, respectively. Our studies reveal the important role of closed-shell (d10) versus open-shell (d0) electronic configurations of the nonmagnetic sites in determining the overall magnetic exchange interactions. Although the magnetic Os5+ (5d³) site is the same in all compounds, the magnetic superexchange interactions mediated by nonmagnetic Y/In/Sc species are strongest for Sr2ScOsO6, weakest for Sr2InOsO6, and intermediate in the case of the Y (d0) due to different energy overlaps between Os-5d and Y/In/Sc-d states. This explains the experimentally observed substantial differences in the magnetic transition temperatures of these materials, despite an identical magnetic site and underlying magnetic ground state. Furthermore, short-range Os-Os exchange interactions are more prominent than long-range Os-Os interactions in these compounds, which contrasts with the behavior of other 3d-5d double perovskites. [ABSTRACT FROM AUTHOR]