Phenomenological description of order-disorder by means of general correlation functions II. Approximation of independent clusters

Abstract

A phenomenological description of order in a two-component material is developed for the case of appreciable clustering. In contrast to the previous part of the paper a macroscopic and continuous (instead of discrete and microscopic) model is used for which the characteristics of order analogous to those of the preceding part are determined. It is assumed that the ordering can be characterized by the distribution of clusters, which form impurity component in the host one. The quantities related to the order are averaged over the ensemble of all possible configurations of clusters conserving the cluster distribution. All such configurations are taken with the same probability, wherefore the term approximation of independent clusters is used. The two-ion correlation function and its Fourier component are calculated in this approximation and their statistical properties are studied, that are useful in the statistical analysis of two-magnon dissipation processes.