Direct observation of polarization mixing in nuclear Bragg x-ray scattering of synchrotron radiation

The direct observation of polarization mixing in nuclear Bragg scattering of synchrotron radiation by α${\mathrm{-}}^{57}$Fe${\mathrm{’}\mathrm{’}}_2$ ${\mathrm{O}}_3$ is reported. Application of a magnetic bias field having the appropriate orientation was shown to produce almost complete rotation of the σ-polarized incident beam to a π-polarized diffracted beam. Rotation of this field about the diffraction vector through 90° caused the diffracted beam polarization to change continuously from σ through elliptical to π, as predicted theoretically.