Thermodynamics of the two-dimensional easy-axis quantum antiferromagnet

Abstract The thermodynamics of the two-dimensional quantum Heisenberg antiferromagnet with easy-axis anisotropy (EA-QHAF) on the square lattice is studied by means of the semiclassical approach of the pure-quantum self-consistent harmonic approximation (PQSCHA). The anisotropic model shows a phase transition at finite temperature with critical exponents of the two-dimensional Ising model for every value of the anisotropy. Our theoretical results are compared with the experimental data on the real compound Rb 2 MnF 4 both above (correlation length) and below (staggered magnetization) the transition: a good agreement is found in both the disordered and the ordered phase.