Orbital ordering and magnetism in layered Perovskite Ruthenate Sr(2)RuO(4)

Local density approximation plus on-site Coulomb interaction U electronic structure calculations reveal that layered perovskite oxide Sr(2)RuO(4) exhibits the ferromagnetic (FM) half-metallic ground state, which is nearly degenerate with the antiferromagnetic (AFM) phase with a slightly higher total energy. The nearly degenerate FM/AFM total energies provide a reasonable explanation for the experimentally observed spin-fluctuation. In addition, a dumbbell-shape 4d − t(2g) recombined d(xz) − d(yz) orbital ordering on the Ru sublattice is obtained owing to the on-site Coulomb interaction U associated with the elongated RuO(6) octahedron local structure. The discovered orbital ordering is robust against the spin-orbit interaction as well as the surface terminations. Our findings unravel the on-site Coulomb correlation as the driving force of the Ru-4d orbital ordering as well as the inherent magnetic degeneracy.