The spin-1/2 ising model with skew magnetic field at high temperatures

Abstract

We calculate the thermodynamics of the one-dimensional spin-1/2 Ising model in the presence of a constant skew magnetic field. We obtain the high-temperature expansion of its Helmholtz free energy (HFE), for the ferromagnetic and antiferromagnetic cases, up to order β7. This expansion permits us to obtain the behaviour of the model for |Jβ ≤ 1, when it cannot be described by its classical version. Among the calculated thermodynamical functions of the model, we have the diagonal elements of the magnetic susceptibility tensor for the transverse and logitudinal Ising models, obtained by taking the limits hz → 0 and hy → 0, respectively, of the β-expansion of the HFE. The y-component of the magnetization and the χyy component of the magnetic susceptibility tensor are almost the same for the antiferro- and ferromagnetic models, at least for J|β ≲ 1; and, χyy is practically independent of the direction of the external magnetic. We also show that, in this region of temperature, the thermodynamics of the Ising model with skew magnetic field and that of an XXZ model with longitudinal magnetic field are not similar.