Polarization Analysis in Synchrotron Mössbauer Reflectometry

A new experimental technique in Mössbauer spectroscopy with Synchrotron Mössbauer Source that
relies on the polarization analysis of reflected radiation has been tested. We have shown that the
dichroic components in resonant spectrum create the scattering intensity with rotated polarization.
The angular dependence for such component in the reflected signal is characterized by a peak near
the critical angle of the total external reflection. In the case of collinear antiferromagnetic interlayer
ordering the "magnetic" maxima on the reflectivity angular curve are formed practically only by
scattering with this rotated polarization. The first experiment on Mössbauer reflectivity with selection of
rotated polarization discovers the predicted peak near critical angle. The measured Mössbauer
reflectivity spectra (R-spectra) with rotated polarization near the critical angle are rather different from
Mössbauer R-spectra, measured without polarization analysis. They have a simpler shape and
contain a smaller number of lines allowing for an improved data interpretation in the case of poorly
resolved spectra. It is shown that Mössbauer R-spectra with the rotated polarization is characterized
by the enhanced surface sensitivity, determined by the "squared standing waves" depth dependence.
Therefore, the new approach has interesting perspectives for investigations of surfaces, ultrathin
layers and multilayers having complicated magnetic structures.