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}-⁵⁷Fe''₂{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.