Modeling of magnetic properties of A2BB′O6 compounds using ab initio and Monte Carlo methods

Ab initio and Monte Carlo simulations are employed to estimate isotropic exchange interactions and Curie temperature of A₂BB′O₆ oxides (A alkaline-earth metal or transition metal and B, B′ transition metals). The dominant (B–B') interactions are antiferromagnetic (AFM) between the first and second nearest neighbors (NN), and these interactions strengthen as the magnetic moments of B and B' increase. Third and fourth NN interactions (B–B or B′–B′) are always weaker than the others. Although B′–B′ interactions induce magnetic frustration if they are AFM, the ground state is always ferrimagnetic. The Curie temperature range spans from 290 K for Sr₂FeOsO₆ to 640 K for Be₂FeOsO₆. Our study reveals that, in the search for a desired high Curie temperature of A₂BB′O₆ oxides, an A cation should be as small as possible, and B, B′ magnetic moments should be as large as possible.