Time-dependent spin-correlation functions in anisotropic systems. I. Infinite-temperature kinetic equations in the presence of a crystal field

We present in this paper the technical tools necessary to derive kinetic equations for anisotropic spin systems with arbitrary spin; to simplify, we limit ourselves to infinite temperature and to the simplest possible crystal-field anisotropy. We also apply this technique to the derivation of explicit, but approximate, kinetic equations for the direct and indirect spin-autocorrelation functions. The solution of these equations will be discussed in another publication. © 1973.SCOPUS: ar.j