Canted ferromagnetism in RuSr₂GdCu₂O₈

First principles calculations using the full-potential linearized augmented plane wave method including intra-atomic noncollinear magnetism have been performed to determine the magnetic structures of RuSr₂GdCu₂O₈. The magnetism clearly arises from the RuO₆ octahedra where the moments on neighboring Ru sites order antiferromagnetically but cant perpendicular to the antiferromagnetic (AFM) axis - and so induce a weak ferromagnetism. The projected Ru moments along the AFM and FM axes result in magnetic moments of 1.16 and 0.99 μ_B, respectively. The results are consistent with the possible coexistence of canted ferromagnetism and superconductivity in the RuSr₂GdCu₂O₈ - inferred from experiments.