Surface stabilisation of the ferromagnetic phase of FeGe2

Electronic and magnetic properties of bulk and films of FeGe2 are investigated within ab initio density functional theory. Bulk structure displays an anti-ferromagnetic ground state with Fe magnetic moment of 1.36μB and a ferromagnetic configuration a few mRy above. Thin films with a few monolayers display a ferromagnetic ground state with a metastable anti-ferromagnetic configuration a few mRy above. A transition from ferromagnetism to anti-ferromagnetism is observed when the thickness of the film is increased. A strong increase of the magnetic moments, up to 2.64μB, on Fe atoms present at the surface is observed.