Ab initio prediction of quadruple perovskites with half-metallic ferrimagnetism and high Curie temperatures*

CaCu₃Fe₂Re₂O₁₂, a quadruple perovskite (QP) with the chemical formula AA’₃B₂B’₂O₁₂, shows half-metallic ferrimagnetism with large magnetization and a high Curie temperature (T_C). Here we investigated a series of QPs using density functional theory and Monte Carlo simulations. We found that all compounds are ferrimagnetic with substituted A²⁺ (A=Ca, Sr, Ba, Pb) ions exhibiting high Tc (above 405 K), and the A³⁺ (A=Sc, Y, La ) substituted ones yielding even higher T_C (above 502 K). By examining interatomic exchange parameters, we found that the antiferromagnetic exchange couplings between Re and Cu as well as Re and Fe are responsible for this very high Curie temperature. For the compounds with A³⁺ substitution, electron doping in bands around the Fermi level dominated by the Re ions strengthen the Re-Cu and Re-Fe exchange interactions, which cause an increase in the T_C. This work demonstrates a design strategy of enhancing the spin ordering temperature by replacing A-site non-magnetic ions.