Thermodynamic properties of the spin-1/2 Heisenberg ferromagnet are calculated by using Handscomb’s Monte Carlo method. Several methods of analyses are used to determine critical properties of the model. For a square lattice we find that the susceptibility diverges exponentially at zero temperature. That is, χ∼exp[b(J/${\mathit{k}}_{\mathit{B}}$T)] with the constant b=4.5±0.5, which is lower than the prediction (b=2π) of a modified spin-wave theory. For the simple-cubic lattice, we find that the critical temperature ${\mathit{k}}_{\mathit{B}}$${\mathit{T}}_{\mathit{c}}$/J=1.68±0.01, and the ratio of the exponents γ/ν=2.0±0.05, which are in good agreement with the estimates of the high-temperature series-expansion method.

• Received 15 October 1990

DOI:https://doi.org/10.1103/PhysRevB.43.11082