First-principles study of electronic and magnetic properties of FeC13-based graphite intercalation compounds

The structural, electronic and magnetic properties of stage-I and -2 FeCl3-based graphite intercalation compounds (GIC5) are studied in the framework of the GGA+U implementation of density functional theory. The intercalation process extends the c-axis remarkably and modulates the band structure of graphite to p-type doped. A linearly dispersing band structure is observed for stage-I GIC. The carrier density shows a weak descending tendency from stage-I GIC to stage-2 GIC. The dependence of the energy level positions of Fe 3d orbitals on parameter U is strong. With the increase of U, the spin-up states move to the deeper energy levels, while the spin-down states move to the shallower energy levels. Stage-I GIC has antiferromagnetic (AFM) order and stage-2 GICs has ferromagnetic (FM) orders at the ground states, and two combinative effects are proposed to explain the origin of the magnetic transformation from stage-I GIC to stage-2 GIC.