DOI:10.5488/CMP.15.13706 arXiv:1009.4078v4
Title:
The high-temperature expansion of the classical Ising model with $S_z^2$ term
Author(s):
| M.T. Thomaz (Instituto de Física, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza s/no, CEP 24210-346, Niterói-RJ, Brazil) , | |
| O. Rojas (Departamento de Ciências Exatas, Universidade Federal de Lavras, Caixa Postal 3037, CEP 37200-000, Lavras-MG, Brazil ) |
We derive the high-temperature expansion of the Helmholtz free energy up to order β17 of the one-dimensional spin-S Ising model, with single-ion anisotropy term, in the presence of a longitudinal magnetic field. We show that the values of some thermodynamical functions for the ferromagnetic models, in the presence of a weak magnetic field, are not small corrections to their values with h=0. This model with S=3 was applied by Kishine et al. [J.-i. Kishine et al., Phys. Rev. B, 74 (2006) 224419] to analyze experimental data of the single-chain magnet [Mn (saltmen)]2 [Ni(pac)2 (py)2] (PF6)2 for T<40 K. We show that for T<35 K the thermodynamic functions of the large-spin limit model are poor approximations to their analogous spin-3 functions.
Key words:
quantum statistical mechanics, one-dimensional Ising model, spin-S models, large-spin limit Ising model, single-chain magnets.
PACS:
75.10.Jm, 05.30.-d, 75.50.Xx
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