Use of an asymmetric wiggler to study the magnetic circular x-ray dichroism of Ni, Ho, and Tb

The asymmetric wiggler, inserted since the end of 1990 on the Super-Aco storage ring in Orsay, has been built to produce a high rate and high flux of circularly polarized soft x rays in the 100–3000 eV range. This insertion device is particularly well suited to measure x-ray absorption spectra corresponding to dipole transitions towards electronic orbitals that are directly responsible for magnetism (3d states of first row transition metals, 4f states of rare earths). In this article we report the first magnetic circular x-ray dichroism spectra obtained with this insertion device. They exemplify the wide prospects of this experimental setup.