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Half-metals have drawn extensive interest due to their unique electronic structure and wide application in spintronics. We report an A-site-ordered quadruple perovskite CeCu3Cr4O12 with half-metallic behaviors using first-principles calculations. Our calculations demonstrate that CeCu3Cr4O12 is a ferrimagnet with a saturated magnetic moment of 7.00 μB f.u.–1. Effective ferrimagnetic interactions are generated from the antiparallel spin arrangement between the A′-site Cu and B-site Cr. The electronic structure analyses reveal that CeCu3Cr4O12 exhibits half-metal performance, which can be attributed to the mixed-valence of B-site Cr. More importantly, a small amount of 4f itinerant electrons are located on the A-site Ce, i.e., both itinerant electron magnetism and localized magnetic moments are observed in the theoretical calculations. The charge distribution in this system is confirmed to be Ce(4−δ)+Cu2+3Cr(3.5+δ)+4O2−12. The physical properties of the AA′3B4O12-type perovskite CeCu3Cr4O12 revealed in this study show that this class of materials shows promise in applications of half-metals. [ABSTRACT FROM AUTHOR]

The direct bandgap nature of semiconductors is crucial for a wide range of optoelectronic devices and energy applications. These materials are mainly concentrated in hybrid organic–inorganic halide perovskites, III–V semiconductors, and monolayer transition metal dichalcogenides. Here, we report an AA′3B2B′2O12-type direct bandgap semiconductor CaCu3Fe2Ta2O12 using spin-polarized density functional theory calculations. The formation energy indicates that this material is thermodynamically preferred under a high-temperature and high-pressure synthetic route, similar to the analog CaCu3Fe2Nb2O12. Effective ferrimagnetic interaction occurs through the antiferromagnetic coupling between the A-site Cu and B-site Fe. More importantly, CaCu3Fe2Ta2O12 exhibits semiconducting behavior with a direct bandgap in the visible range, suggesting that AA′3B2B′2O12-type quadruple perovskites are potential candidate materials in photovoltaics as well as in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Transition metal oxides show rich physical properties which are often influenced by external perturbation. Here, we report by first-principles calculations that strain enables switching of orbital occupancy of Co2+ in La2CoMnO6 and hence modifies electronic structure of La2CoMnO6. We find a metal-insulator transition in La2CoMnO6, which originates from the interplay between the strain induced lattice distortion and electron correlations. Such transition is understood upon the orbital polarization of Co2+, which takes on the dxz/yz character under compression, yet switches to the dx2-y2 character under tension. The orbital switching presented should hold promise for many technological applications. [ABSTRACT FROM AUTHOR]

Within RCu3Mn4O12 (R=Rare earth), besides the expected ferrimagnetic order of Mn and Cu ions below TC1, R magnetic moments also play an important role at lower temperatures TC2, leading to their peculiar magnetic behavior. By first-principles calculation, we found that along the series from La to Lu, TC1 monotonically increased due to the ionic radius (IR) induced chemical pressure, as experimentally observed, while TC2 is closely related to the atomic radius of R. Additionally, the magnetic anisotropy energy (ΔEani) along the series is found to be correlated with the total magnetic moment of R ion. [ABSTRACT FROM AUTHOR]

We report the heat, magnetic, and dielectric properties of La2-xBixCoMnO6 with a series of Bi doping concentrations, focusing especially on the impact of A-site doping on B-site ordering. We demonstrate that the B-site ordering is enhanced via the Bi doping, resulting in a suppressed cluster-glass behavior, larger dielectric constant, and smaller tangent loss. Surprisingly, a pronounced step-like dielectric anomaly turns up near the spin-freezing temperature in the Bi-free oxide, which is suppressed significantly after Bi doping. We attribute the suppression of anomaly to the lessened amount of antisite defects at the B sites and the associated strengthened electronic localization. [ABSTRACT FROM AUTHOR]