High-Temperature Series and Critical Amplitudes for the Spin-Spin Correlations of the Three-Dimensional Ising Ferromagnet

Abstract

High-temperature series for the inverse spin-spin correlation function of the $s=\frac{1}{2}$ Ising ferromagnet are presented for the three cubic lattices. Series are tabulated to twelfth order in $K=\beta J$ in zero magnetic field and to eighth order in finite field. Direct series expansions for the true correlation length are derived. The critical correlations are analyzed for scaling behavior in both position and momentum space. The critical amplitudes which characterize the correlations both at $T_c$ and in the Ornstein—Zernike region are determined. The Fisher—Burford scattering approximant is found to be consistent with the data. Finally, the consequences of the universality hypothesis are formulated for the correlations. Correlation-amplitude data for the three cubic lattices are shown to be in remarkable agreement with a formulation of universality which requires that the free energy in a region of diameter given by the coherence length be scale independent.