  Hard x-ray scattering (HXS) experiments with a photon energy of 100keV were
performed as a function of temperature and applied magnetic field on selected
compounds of the RFe$_3$(BO$_3$)$_4$ family. The results show the presence of
several unexpected diffraction features, in particular non-resonant magnetic
reflections in the magnetically ordered phase, and structural reflections that
violate the diffraction conditions for the low temperature phase $P3_121$ of
the rare-earth iron borates. The temperature and field dependence of the
magnetic superlattice reflections corroborate the magnetic structures of the
borate compounds obtained by neutron diffraction. The detailed analysis of the
intensity and scattering cross section of the magnetic reflection reveals
details of the magnetic structure of these materials such as the spin domain
structure of NdFe$_3$(BO$_3$)$_4$ and GdFe$_3$(BO$_3$)$_4$. Furthermore we find
that the correlation length of the magnetic domains is around 100 \AA{} for all
the compounds and that the Fe moments are rotated $53^\circ\pm3^\circ$ off from
the hexagonal basal plane in GdFe$_3$(BO$_3$)$_4$
