Electronic structure and magnetism for FeSi (1−x) Ge x from supercell calculations

Abstract Recent studies of FeSi ( 1 - x ) Ge x , which found a transition from an insulating to a magnetic metallic state near x = 0.25 , have revived the discussion about the role of strong correlation in these systems. Here are spin-polarized band calculations made for 64-atom supercells of FeSi ( 1 - x ) Ge x for different x and different volumes for large x . The results show that the small band gap in FeSi is closed for x ⩾ 0.3 , because of both substitutional disorder and increased volume. Ferromagnetism appears near this composition and becomes enforced for increasing x . The x -dependence of the electronic specific heat can be understood from the exchange splitting of the density-of-states near the gap. Strong volume dependencies for the properties of FeGe suggest experiments using pressure instead of x for investigations of the gap.