I have worked on this topic only during my stay as visiting scientist at the ESRF in 1992 and shortly afterwards. Nevertheless, I am very proud of this work:

X-Ray Resonant Magnetic Scattering from Surfaces A. Fasolino, P. Carra, M. Altarelli, Phys. Rev. B 47, 3877 (1993);J. Magn. and Magn. Mat. 121, 194 (1993).
X-Ray resonant exchange scattering from 3d transition metal surfaces G.P. M. Poppe, A. Fasolino, Surf. Sci. 331-333, 1186 (1995).

We have proposed that X-ray resonant magnetic scattering could be combined with X-ray surface crystallography to get information on the magnetic surface structure. In analogy to the crystal truncation rods, one may also define magnetic truncation rods aligned along the surface normal and passing through the magnetic bulk Bragg reflections.

In 1992, intense light sources like the ESRF were not yet operational and the local scientists were very skeptical about the possibility to observe such pure magnetic crystal truncation rods. The very weak intensity of magnetic truncation rods together with the need to work at very specific wavelengths at resonance with a transition from a core level seemed an overwhelming challenge. In 1996, in the Phys. Rev. Lett. 77 of july 22, two papers reported the observation of surface resonant magnetic scattering.

Our derivation of the formula for the scattering cross section for X-ray Resonant Exchange Scattering (XRES) as first given by: J. P. Hannon, G. T. Trammell, M. Blume and D. Gibbs, Phys. Rev. Lett. 61 ,1245 (1988); 62, 2644(E) (1989). It is not straightforward, please let us know if you find it useful.