Magnetic compton scattering with circularly polarised synchrotron radiation

Abstract

The spin-dependent momentum distributions in iron and a few other ferromagnets have now been measured with circularly polarised radiation in the 30–60 keV energy range, obtained by viewing the tangent point of the Daresbury Synchrotron wiggler line at a small angle (<0.2 mrad) to the orbital plane. Even at four times the critical energy of the wiggler, radiation with 70% circular polarisation can be selected and scattered beam count rates approaching 10 3 achieved by matching the monochromator pass band to the resolution of the solid state detector. New data on ferromagnetic iron show a smaller negative polarisation effect than the earlier experiments, in line with recent measurements elsewhere, but the central dip remains larger than either the APW or KKR predictions. Recently the anisotropy in the spin-dependent momentum distribution has been measured in a new experiment using transmission geometry and this shows that the disagreement is strongly associated with the [100] projection direction.