No abstract

Using the mean field theory, the effect of a transverse magnetic field on the layering and wetting transitions of the spin‐1/2 Ising model with longitudinal magnetic field is studied. At a fixed value of the temperature smaller than the wetting temperature, such system exhibits a sequence of layering transitions above a critical value of the transverse magnetic field, which depends on the temperature and surface magnetic field.

The thermodynamics properties of a ferromagnetic Heisenberg model with the exchange anisotropy of a spin-1 system in presence of single-ion anisotropy (D) and external magnetic field (h) are studied here using the pair approximation approach. We treat the model in three-dimensional lattice with coordination number z=6. Other coordination numbers have been also examined. Within this approximation based on Gibbs free energy, we investigate the effect of both single-ion and exchange coupling anisotropies on the thermodynamic quantities such as magnetization, entropy, heat capacity, susceptibility and entropy change as in-process measures. The objective is to describe magnetocaloric effect (MCE) and relative cooling power aiming to optimize them. We find some interesting phenomena in these quantities due to external magnetic field, exchange anisotropy and single-ion anisotropy. For conflicting interactions, re-entrance behavior can occur. Interestingly, high spin size as well as strong exchange or single-ion anisotropy can improve the MCE performances. PA method [8,9]. It is clear from the above matrix elements that the matrix representation of H ij in this base is symmetric. Therefore, we need to determine the eigenvalues by diagonalizing the matrix of H . ij After performing calculations, we find the following eigenvalues: E J D D J J 2.4. Critical temperature The Curie temperature T C can be found by linearization of self-consistent equation (20) when 0 l  and external magnetic field h=0, leading to: z z J J w 1 2 e 2e cosh e 2e 4 cosh 2e cosh , 2 7 D J D J D J D J

No abstract

No abstract