Intensities of Mössbauer diffractions from polycrystalline bcc 57 Fe

Diffraction patterns were measured on a polycrystalline bcc Fe foil using a Mössbauer powder diffractometer with high sensitivity. Measurements with and without a magnetic field normal to the scattering plane showed large differences in the diffracted intensities of the different nuclear resonances. These magnetic effects on diffraction intensities were interpreted successfully with a single scattering theory developed to handle isotropic and anisotropic orientation distributions of hyperfine magnetic fields. When there is coherent interference between nuclear scattering and x-ray Rayleigh scattering, an asymmetry in the coherent intensity of the three pairs of diffractions for the Fe magnetic sextet ~1,6!, ~2,5!, ~3,4! is predicted. This is largest in the presence of a uniaxial magnetic field, and the calculated and measured asymmetries were in good agreement. A reduced diffraction intensity for lines ~2,5! and ~3,4! caused by spin-flip incoherence was also measured. The effects of dynamical diffraction, if present, are shown to be small.