Magnetic X-ray dichroism in the soft X-ray energy range: application to the study of magnetism in intermetallic and modulated (multilayers, superlattices) systems

Magnetic X-ray dichroism (MXD) is related to the dependence of the absorption cross-section of a given atom (with well-defined angular momentum) on the state of polarization of light. Synchrotron radiation (SR) sources, because of their well-defined states of polarization, their high-flux and high brilliance, are thus ideal to perform MXD experiments even when the total number of absorbing atoms does not exceed 1015, which is interesting in the case of surface magnetism. We consider how the magnetic absorption cross-section may be directly related to the local magnetic properties of the absorbing atom via spin-orbit coupling and exchange interactions. Taking benefit of selection and sum rules, the ability to separate both the contributions to the total angular momentum (i.e. the magnetic moment) of individual electronic shells (s, p, d, f) and the spin contribution from the orbital one is shown. (orig.)