Here the initial conditions are set to assure a single domain of the dipolar antiferromagnet at low temperature. Running at a temperature of 0.8 you see occasional thermal fluctuations of individual spins, and no preference of up versus down spins in these fluctuations. Now, as you run again, click on the slot of the external field slider to increase H to 0.5 or 1.0, watching the "color" of the excitations as you change the field. (And click back down to negative field.) Note from the graph a rough value of the magnetization induced by a field of H = 1.
Reduce T to 0.2. Now what magnetization is produced by a field H = 1? The susceptibility you've observed here is analogous to the "parallel susceptibility" of a three dimensional antiferromagnet which goes to zero as the temperature goes to zero.
You can try to overwhelm the antiferromagnetic coupling by changing the external field to H = 5. You see a new ordered phase of the system. If this were allowed to anneal to a single domain, what would be the associated magnetization?