The Effects of Broadening on the High Temperature Critical Susceptibility Exponent g

Abstract

A theoretical study of the effects of a distribution of ordering temperatures Tc on the high temperature critical susceptibility exponent y is described. Analytical and numerical solutions for yare derived for the fitting of broadened susceptibility data to the critical equation X = Xo{(T- Tc)/Tc}-'. Both least squares fitting and Kouvel-Fisher analyses are considered. Using a simple model for magnetically inhomogeneous material it is shown that the inclusion of the internal demagnetizing fields greatly reduces the effect of the broadening upon the deduced critical exponent. Theory is compared with experiment for the critical susceptibility of gadolinium.