Magnetic and electronic structures of superconducting RuSr2GdCu2O8 - art. no. 024507

The coexistence of ferromagnetism and superconductivity in RuSr2GdCu2O8 was reported both from experiments (by Tallon et al.) and first-principles cal culations (by Pickett et al.). Here we report that our first principles ful l-potential linearized augmented plane wave calculations, employing the pre cise crystal structure with structural distortions (i.e., RuO6 rotations) d etermined by neutron diffraction, demonstrate that antiferromagnetic orderi ng of the Ru moments is energetically favored over the previously proposed ferromagnetic ordering. Our results are consistent with recently performed magnetic neutron diffraction experiments (Lynn et al.). Ru t(2g) states, wh ich are responsible for the magnetism, have only a very small interaction w ith Cu e (g) states, which results in a small exchange splitting of these s tates. The Fermi surface, characterized by strongly hybridized dp sigma orb itals, has nesting features similar to those in the two-dimensional high-T- c cuprate super conductors.