  We have developed the extension of the exact x-ray resonant magnetic
reflectivity theory taking into account the small value of the magnetic terms
in the x-ray susceptibility tensor. We have shown that squared standing waves
(forth powder of the total electric field module) determine the output of the
magnetic addition to the total reflectivity from a magnetic multilayer. The
approach gives the easily understandable results especially for the
reflectivity part with the rotated polarization and the obtained relationship
can essentially speed up the calculation of the asymmetry ratio of the magnetic
reflectivity relative the sign of the circular polarization in the incident
radiation. The connection of the magnetic contribution with the standing wave
structure in the magnetic multilayer means that the magnetic reflectivity with
rotated polarization possesses higher sensitivity to the depth profiles of
magnetization and magnetic elements depth distribution than the secondary
radiation registration at the specular reflection condition.
