Hard x-ray scattering experiments with a photon energy of 100 keV were performed as a function of temperature and applied magnetic field on selected compounds of the R Fe₃(BO₃)₄ family. The results show the presence of several diffraction features, in particular, nonresonant magnetic reflections in the magnetically ordered phase and structural reflections that violate the diffraction conditions for the low-temperature phase P 3₁ 21 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 NdFe₃(BO ₃)₄ and GdFe₃(BO₃)₄. Furthermore we find that the correlation length of the magnetic domains is around 100 Å for all the compounds and that the Fe moments are rotated 53°±3° off from the hexagonal basal plane in GdFe ₃(BO₃)₄.