Comparison of the ferromagnetic Blume-Emery-Griffiths model and the AF spin-1 longitudinal Ising model at low temperature

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:401

Article

Thomaz, M. T.¹  Correa Silva, E. V.² 

[1] Univ Fed Fluminense, Inst Fis, BR-24210346 Niteroi, RJ, Brazil

[2] Univ Estado Rio de Janeiro, Dept Matemat Fis & Comp, Fac Tecnol, BR-27537000 Resende, RJ, Brazil

关键词: Quantum statistical mechanics;    Blume-Emery-Griffiths model;    BEG model;    Ising model;    Spin-1;    Staggered;    Thermodynamics;    Optical device;   

DOI  :  10.1016/j.jmmm.2015.10.071

来源: Elsevier

【 摘 要 】

We derive the exact Helmholtz free energy (HFE) of the standard and staggered one-dimensional Blume-Emery-Griffiths (BEG) model in the presence of an external longitudinal magnetic field. We discuss in detail the thermodynamic behavior of the ferromagnetic version of the model, which exhibits magnetic field-dependent plateaux in the z-component of its magnetization at low temperatures. We also study the behavior of its specific heat and entropy, both per site, at finite temperature. The degeneracy of the ground state, at T=0, along the lines that separate distinct phases in the phase diagram of the ferromagnetic BEG model is calculated, extending the study of the phase diagram of the spin-1 antiferromagnetic (AF) Ising model in S.M. de Souza and M.T. Thomaz, J. Magn. and Magn. Mater. 354 (2014) 205 [5]. We explore the implications of the equality of phase diagrams, at T=0, of the ferromagnetic BEG model with K/vertical bar J vertical bar = -2 and of the spin-1 AF Ising model for D/vertical bar f vertical bar > 1/2. (C) 2015 Published by Elsevier B.V.

【 授权许可】

Free