Magnetic and electronic structure in new iron-based layered SrFe1 − xCoxAsF systems

By using the first-principles calculation, we study the structural, magnetic, and electronic properties of the SrFeAsF compound and its Co-doped counterpart SrFe1 − xCoxAsF (x=0.125). It is shown that the competition of the nearest and next-nearest neighbor exchange coupling J1 and J2 between Fe ions gives rise to a frustrated striped antiferromagnetic order in SrFeAsF and an accompanied lattice distortion, while for the Co-doped case, both J1 and J2 decrease significantly as well as the lattice distortion, and thus the antiferromagnetic order is suppressed greatly. This is further confirmed by the electronic structure calculation that the density of states at the Fermi level increases with Co doping as well as the itinerancy of Fe d electron.