Magneto-optical activity of rare earth ions near the M4,5 absorption edges

The absolute values and frequency dependences of the contributions to the diagonal part, gyrotropy g, and anisotropy δ parameters of dielectric tensor \̂ge forced by resonant 3d10 4fn → 3d9 4fn + 1 dipole-allowed transitions have been calculated using a minimum approximation approach for all rare earth ions (REI). The magnitudes of g and δ are shown to reach giant values, of the order of 5 × 10−3, being comparable with the nonmagnetic diagonal part. These results may be used for the description of the magneto-optical effects near the M4,5 edges of REI and show the possibility of observing dynamical diffraction effects in direct soft X-ray diffraction on magnetic (e.g. spiral) structures.