The initial susceptibility of Heisenberg antiferromagnetic square lattice

The temperature dependence of the initial magnetic susceptibility of plane square lattice with antiferromagnetic Heisenberg exchange interaction for S = 1/2 was calculated. The temperature Green's function method with decoupling in the second order was used. The susceptibility was determined numerically in the whole temperature range. The asymptotic analytical expressions for the cases of low and high temperatures were obtained. At low temperatures the susceptibility grows from the finite value at the absolute zero of T proportionally to T-3. At high temperatures the susceptibility has the form of a series in the inverse T powers and approaches asymptotically the Curie-Weiss law. The results of calculations are compared with the experiments. The conclusions of this paper are compared with the theoretical investigations of other authors.