X-Ray grazing-incidence magneto-optics of multilayer structures under 
resonant spectral conditions

V.M.Matveev, V.V.Matveev

State Research Institute of Physical Problems,
103460, Zelenograd, Moscow, Russia

Giant grazing-incidence polarization phenomena at resonant reflection of 
soft X-rays from rare earth magnetic superlattices have been examined 
theoretically. The unique combination of the grazing-incidence geometry 
and the 3d-4f atomic resonance with the well-known resonant enhancement of 
magneto-optical activity of rare earth elements near M absorption edges is 
shown to result in the strong dependence of grazing-incidence reflection 
amplitudes on the polarization state of an incoming X-ray beam and the 
magnetic state of a reflecting surface layer. Near the critical angle of 
total external reflection, the corresponding relative magneto- and 
polarization-sensitive variations of X-ray reflectivity and Kerr effect 
values may reach of about 80% and are easily detectable. At small glancing 
angles, the Kerr effect behavior is unique in relating not only to the 
sharp distinctions between the p and s reflectivities, but also to the 
large difference in phase between the p and s reflection amplitudes.

All this, taking into account the small tunable penetration depth (1
-200 nm) of soft X-rays under discussed condition, allows us to put
forward the "double-anomalous" magneto-optics as a fruitful method for
determination of the depth profiles and interface distributions of
magnetization in magnetic films and superlattices with a high degree
of accuracy. For example, as the depth profile consists in the
rotation of a magnetization vector in a surface layer from in-plane to 
normal direction, a reflectivity change of a few percent may be observed 
when the width of the layer varies over 10%. The values of the basic 
structural magnetic and non-magnetic parameters of superlattices are 
easily derived from reflectivity and Kerr effect values as well. A new 
method to attack the problem of determination of these parameters from 
reflectivity measurements based on the direct use of the fundamental Bloch 
solutions of the Maxwell's equations is developed. Diffraction phenomena 
in "spiral" rare earth superlattices are examined.

New optical elements with magnetic control for synchrotron radiation 
beamlines using polarization-sensitive "double-anomalous" reflection from 
rare earth superlattices are discussed. Such elements - polarization 
filters, convertors and switches - provide high conversion and filtration 
efficiency with intensity losses of about 30%.