Ab Initio Study of Magnetism in FeSe and FeTe

Magnetism in FeSe and FeTe systems is studied using density functional theory. Nonmagnetic (NM), ferromagnetic (FM) and three different antiferromagnetic (AFM) states are considered. We have investigated chalcogen height dependence of magnetism using LDA and GGA exchange correlations. For FeSe, LDA used for both structural optimization and magnetism, yields magnetic energies that seem close to experiments. For FeTe, LDA and GGA give different magnetic ground states for experimental zTe. For FeTe, GGA gives magnetic ground state that is found in experiments, which is in contrast to FeSe and pnictides.