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High Temperature Expansions of Spin Correlation Functions for Ising and Heisenberg Ferromagnets
Author(s) -
Binder K.
Publication year - 1969
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.19690320243
Subject(s) - ising model , cubic crystal system , condensed matter physics , anisotropy , ferromagnetism , lattice (music) , physics , cluster expansion , heisenberg model , spin (aerodynamics) , cluster (spacecraft) , statistical physics , quantum mechanics , thermodynamics , computer science , acoustics , programming language
Linked cluster expansions are given for the static spin pair correlation functions in the case of Ising and Heisenberg interactions. Formulae valid for general values S of the spin are derived including terms of fifth order in 1/( kT ). These expansions are discussed numerically in the temperature region T c / T ≦ 1/2 for the simple cubic, the body‐centered cubic and the face‐centered cubic lattice assuming interactions between nearest neighbours only. A comparison with the usual Ornstein‐Zernike treatments shows considerable deviations due to the anisotropy of the correlations. This anisotropy can be neglected only in the immediate neighbourhood of the critical temperature T c .