Structural, electronic, and magnetic properties of the europium chalcogenides: A hybrid-functional DFT study

We analyze the structural, electronic, and magnetic properties of the europium chalcogenide series EuX (X = O, S, Se, and Te) using density-functional theory (DFT). To describe the localized 4f states of Eu, we utilize the parameter-free PBE0 and HSE hybrid functionals and found a systematic qualitative and quantitative improvement over the conventional local and semilocal functionals. Both hybrid functionals predict the lattice constant and the bulk modulus of all four compounds accurately. The semiconducting behavior, the opening of the band gap, as well as the nature of the band gap across the series is reproduced. By mapping the magnetic interactions to a Heisenberg model up to the next-nearest neighbors, we find the correct trend of the magnetic order of the Eu compounds (in magnetic coupling of the Eu 4f moments), from ferromagnetic in EuO to antiferromagnetic in EuTe, with critical temperatures that are in fair agreement with experiment.