Green's Function Theory of Magnetic Relaxation. I

Abstract

It is shown that the method of two-time Green's function may be used as a systematic way of investigating the behaviour of relaxation in magnetic materials. A stochastic assumption has been introduced to terminate the chain of higher order Green's functions. As a result the macroscopic parameter of relaxation in a localized spin assembly is expressed by the interaction constant and the spatial correlation of spin deviations at a single time in an equilibrium assembly. The temperature dependence of the latter quantity may also be calculated by the same method. Only the general formulation is presented in part I, and examples will be given in subsequent publications on the width of resonance in ferro- and antiferromagnetic substances.