Critical behavior of a plane Ising antiferromagnet with two-dimensional dipole interaction

For the antiferromagnetic Ising model on a square lattice with two-dimensional purely dipole interaction, seven terms are calculated in the high-temperature expansions of the susceptibility with respect to an inhomogeneous field with the period of the ground state and of the energy. The estimate of the critical exponent of the susceptibility with respect to the inhomogeneous field, $\gamma=1,00\pm0,05$, shows that the model and the Ising model with shortrange interaction belong to different universality classes. The estimates of the critical temperature and the Curie–Weiss constant differ by more than a factor two from the predictions of the molecular field approximation. The values of the energy and entropy at the critical point indicate that there are strong correlation effects in the paramagnetic phase.