CALCULATION OF X-RAY MAGNETIC CIRCULAR-DICHROISM IN GD

An approximate theory for x-ray magnetic circular dichroism (XMCD) is presented for the special case of half-filled shells, e.g., Gd. The L(2) and L(3) XMCD structure arises primarily from the exchange interaction of the photoelectron and provides a test of various exchange models. The XMCD signal can be interpreted in terms of an effective magnetic scattering amplitude that depends on the spin of the absorber and of the scattering atoms. Ab initio curved-wave multiple-scattering calculations for the La and LQ edges of Gd are found to be in satisfactory agreement with experiment.