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Acta Physica Sinica

CRITICAL TEMPERATURE CURVES FOR THE GENERALIZED MIXED SPIN MODEL

WANG FU-GAO, HU JIA-ZHEN, 上海交通大学应用物理系凝聚态物理研究所,上海200030

Published Jan 1, 1993• 1 citation
Publisher

Abstract

In this paper, we propose a generalized mixed spin model on the union jack lattice. The mean field. free-fermion approximations and equiscale transformation in the same universality class method are applied to this model. The critical temperature curves obtained by different methods agree with each other quite well. We also compare the three different methods. In some special cases, the same critical points as in exactly solved models are obtained.

DOI
10.7498/aps.42.1179-2

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Acta Physica Sinica•Jan 1, 1988•0 citations
In this paper, we propose a generalized mixed spin model on the union jack lattice. The mean field. free-fermion approximations and equiscale transformation in the same universality class method are applied to this model. The critical temperature curves obtained by different methods agree with each other quite well. We also compare the three different methods. In some special cases, the same critical points as in exactly solved models are obtained.
Abstract The mixed spin‐1/2 and spin‐3/2 Ising model on the Union Jack lattice is solved by establishing a mapping correspondence with the eight‐vertex model. It is shown that the model under investigation becomes exactly soluble as a free‐fermion eight‐vertex model when the parameter of uniaxial single‐ion anisotropy tends to infinity. Under this restriction, the critical points are characterized by critical exponents from the standard Ising universality class. In a certain subspace of interaction parameters, which corresponds to a coexistence surface between two ordered phases, the model becomes exactly soluble as a symmetric zero‐field eight‐vertex model. This surface is bounded by a line of bicritical points having interaction‐dependent critical exponents that satisfy a weak universality hypothesis. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)