Hi,
Thank you for your reply. I am only interested in the case with B=0.
The expression for the magnetization is [itex]M=[1\sinh^{4}(2/k_B T)]^{1/8}[/itex].
The susceptibility is obtained from [itex]\chi = \frac{<M^2> <M>^2}{k_B T}[/itex].
But I don't know the analytical expression for [itex]\chi[/itex]...
