Gaussian Fluctuations of Two Molecular Fields in the Blume-Emery-Griffiths Model
W. Jaworski and Z. Jacyna-Onyszkiewicz
Quantum Physics Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 PoznaƄ, Poland
Received: October 6, 2010; in final form: January 5, 2011
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The Blume-Emery-Griffiths model for spins S=1 in a bilayer with z=5 nearest neighbours is studied with the use of Gaussian fluctuations approximation. The fluctuations of two molecular fields, connected with two order parameters, are introduced. Their influence on phase diagrams for non-negative values of the biquadratic coupling constant is taken under consideration. The results are compared with those obtained by the mean-field approximation and discussed.
DOI: 10.12693/APhysPolA.119.846
PACS numbers: 75.10.Dg, 75.10.Hk, 75.10.Jm