Ising Model in a Magnetic Field

Seung‐Yeon Kim, Wooseop Kwak

The partition function zeros of the Ising model on a kagomé lattice in the complex magnetic-field plane are obtained. The properties of the Ising model on a kagomé lattice are not known in an external magnetic field. We estimate the joint density of states for the Ising model on a kagomé lattice in an external magnetic field by using the Wang-Landau sampling method. From the joint density of states, we evaluate its partition function zeros (so-called the Yang-Lee zeros) in the complex magnetic-field plane. For the first time, we investigate the unknown properties of the Ising model on a kagomé lattice in an external magnetic field by using its Yang-Lee zeros.

A. Benyoussef, T. Biaz, M. Touzani

Jonathan V. Selinger

Martin S. Kochman'ski

The paper presents new method for calculating the low-temperature asymptotics of free energy of the 3D Ising model in external magnetic field (H = 0). The results obtained are valid in the wide range of temperature and magnetic field values fulfilling the condition: [1 − tanh(h/2)] ∼ ε, for ε ≪ 1, where h = βH, β- the inverse temperature and H- external magnetic field. For this purpose the method of transfer-matrix, and generalized Jordan-Wigner transformations, in the form introduced by the author in [1], are applied. PACS number(s): 05.50. +q Typeset using REVTEX 1 I. FORMULATION OF THE PROBLEM As is well known, till now an exact solution for the 2D Ising model in external magnetic field (H = 0) was not found. In the case of the 3D Ising model there does not exist an exact solution forvanishing magnetic field (H = 0), without even mentioning the case with magnetic field. Despite great successes in investigations of the Ising model reachedusing

E.V. Corrêa Silva, S. M. de Souza, Onofre Rojas +2 more

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 beta7. This expansion permits us to obtain the behaviour of the model for $ |J| \beta \stackrel {<}{_\sim}} 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 h z -> 0 and h y -> 0, respectively, of the beta-expansion of the HFE. The y-component of the magnetization and the chiyy component of the magnetic susceptibility tensor are almost the same for the antiferro- and ferromagnetic models, at least for $ |J| \beta \stackrel {<}{_\sim}} 1 $; and, c yy 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.

Geoffrey Grimmett