Can dynamical effects in magnetic X-ray diffraction on spiral magnetic structures be observed?
Strong X-ray resonant magnetic scattering near the M absorption edges of rare earth elements results in a drastic decrease in the magnetic extinction length, which becomes comparable to the absorption length. Under such conditions it may be possible to observe dynamical effects in direct X-ray diffraction on spiral magnetic structures in rare earth magnets. A dynamical theory of X-ray diffraction on a simple magnetic spiral is presented. Diffraction properties of spiral magnets are shown to be similar to the well-known unique properties of liquid crystals (such as cholesterics), but the magnetic nature of the spiral leads to more complex diffraction phenomena. Diffraction on spiral magnets shows both ‘cholesteric’ and ‘gyrotropic’ (magnetic) features: two types of reflections with different polarization properties at different Bragg angles may be observed. The region of magnetic reflection is shown to have a complex angular and polarization structure. Specific ‘elliptical’ standing wav
