Two-Particle Cluster Theory of Antiferromagnetism

摘要

The two-spin cluster theory of Strieb, Callen and Horwitz, is extended to antiferromagnets. The theory is formulated to include nearest and next-nearest neighbor exchange (J sub 1 and J sub 2) and to apply to those types of antiferromagnetic Neel phases in which equal numbers of spins are nominally 'up' and 'down'. When J sub 2 = 0 the theory reduces to the antiferromagnetic constant coupling theory of Kasteleijn and van Kranendonk. Consequently the theory suffers from the defect of an anti-Neel transition at low temperatures. (Author)