Condensed Matter Physics, 2012, vol. 15, No. 1, 13706: 110
DOI:10.5488/CMP.15.13706
arXiv:1009.4078v4
Title:
The hightemperature 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/n^{o}, CEP 24210346, NiteróiRJ, Brazil)
,


O. Rojas
(Departamento de Ciências Exatas, Universidade Federal de Lavras, Caixa Postal 3037, CEP 37200000, LavrasMG, Brazil )

We derive the hightemperature expansion of the Helmholtz free energy up to order β^{17} of the onedimensional spinS Ising model, with singleion 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 singlechain magnet [Mn (saltmen)]_{2} [Ni(pac)_{2} (py)_{2}] (PF_{6})_{2} for T<40 K. We show that for T<35 K the thermodynamic functions of the largespin limit model are poor approximations to their analogous spin3 functions.
Key words:
quantum statistical mechanics, onedimensional Ising model, spinS models, largespin limit Ising model, singlechain magnets.
PACS:
75.10.Jm, 05.30.d, 75.50.Xx
