  Quantitative analyses of x-ray scattering from thin films of Ho and Dy metal
at the M_5 resonances result in values of the optical constants and the
magnetic scattering lengths f_m, with f_m as large as 200 r_0. The observation
of first- and second-order magnetic satellites allows to separate f_m into
circular and linear dichroic contributions. This high magnetic sensitivity, in
conjunction with the tunable x-ray probing depth across the resonance can be
applied to monitor depth profiles of complex magnetic structures, as e.g. of
helical antiferromagnetic domains in a Dy metal film.
