Thermodynamics properties of an anisotropic Ising antiferromagnet in both external longitudinal and transverse fields

We have studied the anisotropic two-dimensional nearest-neighbor Ising model with competitive interactions in both uniform longitudinal field H and transverse magnetic field Ω . Using the effective-field theory (EFT) with correlation in cluster with N = 1 spin we calculate the thermodynamic properties as a function of temperature with values H and Ω fixed. The model consists of ferromagnetic interaction J x in the x direction and antiferromagnetic interaction J y in the y direction, and it is found that for H / J y ∈ [ 0 , 2 ] the system exhibits a second-order phase transition. The thermodynamic properties are obtained for the particular case of λ = J x / J y = 1 (isotropic square lattice).