Role of spin-orbit coupling in canted ferromagnetism and spin-wave dynamics of SrRuO3

A canted ferromagnetic arrangement with a long-range-ordered antiferromagnetic component is predicted for the metallic SrRuO3 orthoperovskite based on local-density-approximation-type electronic-structure calculation including on-site Coulomb repulsion U and spin-orbit coupling. The electronic state of Ru4+ ions and the nature of nonzero orbital momentum are analyzed in detail. With regard to the density of states at the Fermi level, the value of the magnetic moment, and the easy axis along the a-axis in a Pbnm setting, a good agreement with the experimental data is achieved for U = 1 eV. The calculated parameters of magnetic exchange, including the anisotropic and antisymmetric terms, are used to determine the magnon spectra. It is shown that notable anisotropic exchange in SrRuO3 is responsible for a gap of 1.7 meV at the Gamma point of the magnon spectra, found previously by inelastic neutron diffraction. The origin of the spin canting that is confined within the ab-plane follows from the presence of the Dzyaloshinskii-Moriya interaction associated with the antisymmetric exchange.