THEORY OF EXCHANGE COUPLING IN MAGNETIC MULTILAYERS

Two layers of magnetic materials separated by a nonmagnetic ''spacer'' layer display an exchange coupling between the separated magnetic lay ers, as detailed by the papers on experimental aspects of magnetic mul tilayers in this issue. Here we describe from a personal perspective t he current theoretical understanding of exchange coupling in magnetic multilayers. The understanding by this point is quite good, and involv es contributions from a number of authors, of which we review a key su bset. The organization of the paper is as follows. After an introducti on to RKKY coupling, the next section discusses the effects of a reali stic band structure (with emphasis on the work of Herman et al., Bruno and Chappert, and Stiles). The following section, which introduces qu antum wells, covers the work of Mathon et al., Bruno et al., and this author. Finally, we include a discussion of the predictability of ampl itude, period, and phase, including the effects of disorder.