  First principles calculations using the full-potential linearized augmented
plane wave (FLAPW) method including intra-atomic noncollinear magnetism have
been performed to determine the magnetic structures of
RuSr$_{2}$GdCu$_{2}$O$_{8}$. The magnetism clearly arises from the RuO$_{6}$
octahedra where the moments on neighboring Ru sites order antiferromagnetically
but cant perpendicular to the 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 $\mu_{B}$ respectively. The results are consistent with the
possible coexistence of canted ferromagnetism and superconductivity in the
RuSr$_{2}$GdCu$_{2}$O$_{8}$ - inferred from experiments.
