Magnetism of 3d transition metal/germanium compounds with Al2Cu structure

Ab initio density functional theory is used for the determination of the electronic and magnetic properties of XGe2 (X=Mn, Fe, Co) ordered compounds. FeGe2 displays an antiferromagnetic ground state with Fe magnetic moment of 1.43 μB and a ferromagnetic configuration a few mRy above. For MnGe2 it is difficult to see whether the ground state is non-magnetic or antiferromagnetic because the difference of energy between them is marginal. The ferromagnetic configuration is metastable but a slight increase of the lattice parameter stabilizes it. No magnetic configuration is obtained for CoGe2 even with a slight increase of the lattice parameter. We report also some preliminary results of germanium based compounds with two different chemical types chosen between Mn, Fe and Co. The magnetic arrangements obtained are correlated to the relative positions of the magnetic atoms.