Theories of Compton Scattering by Magnetic Materials *

Radiat ion scattering experiments on magnetic materials cont inue to provide new and exciting science. Recent examples include polar izat ion and resonance studies of x-ray magnet ic scattering in rare-earth metals [1] and white-beam nonresonant diffraction of synchrot ron radia t ion f rom ferromagnet ic iron [2]. Mater ia l propert ies probed in such experiments are weak s t ructural modula t ions tha t accompany the magnet ic order ing of some rare-ear th metals and that are described by a so-called spin-slip model, and the spin and orbi tal contr ibut ions to the magneticmomen t dis tr ibut ion. F o r the mos t par t , neut ron scattering is the preferred method for the study of magnetic configurat ions, s tructures a n d excitations. N o t able a m o n g recent achievements is the confirmat ion of an interplay between spin and orbi tal moments in actinide c o m p o u n d s [3, 4]. There are fresh challenges, to bo th experimental and theoret ical methods, presented by the development of new magnet ic materials with at tract ive propert ies for appl icat ions in various devices [5]. In the present paper we gather results for C o m p t o n and total scattering of pho tons by magnet ic materials. Discussions are at a basic level in as much that no specific experimental da ta are analysed. Rather , key elements of s t anda rd theoretical models are summarized and compared . Hence, we begin by recording the cross-section for p h o t o n scattering by a free polarized electron initially at rest, a result tha t is an ou tcome of