A CLUSTER VARIATION APPROACH TO THE RANDOM-ANISOTROPY BLUME-EMERY-GRIFFITHS MODEL

Citation
C. Buzano et al., A CLUSTER VARIATION APPROACH TO THE RANDOM-ANISOTROPY BLUME-EMERY-GRIFFITHS MODEL, Journal of physics. Condensed matter, 6(2), 1994, pp. 327-338
Citations number
16
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
09538984
Volume
6
Issue
2
Year of publication
1994
Pages
327 - 338
Database
ISI
SICI code
0953-8984(1994)6:2<327:ACVATT>2.0.ZU;2-S
Abstract
The random-anisotropy Blume-Emery-Griffiths model, which has been prop osed to describe the critical behaviour of He-3-He-4 mixtures in a por ous medium, is studied in the pair approximation of the cluster variat ion method extended to disordered systems. Several new features, with respect to mean-field theory, are found, including a rich ground state , a non-zero percolation threshold, a reentrant coexistence curve and a miscibility gap on the high-He-3-concentration side down to zero tem perature. Furthermore, nearest-neighbour correlations are introduced i nto the random distribution of the anisotropy, and are shown to be res ponsible for the raising of the critical temperature with respect to t he pure and uncorrelated random cases and to contribute to the detachm ent of the coexistence curve from the lambda line.