I'm doing a computational physics project where I'm looking at the Ising model in 2D and external magnetics field. I start with all the spins in same directions my grid is 30x30 and I use periodic boundry conditions. I start with all the spins in the same direction (+1). I do about 150000 scans with Metropolis algorithm at every temperature so it can reach thermal equilibrium and then I collect data for 350000 scans after that. So my question is: When I apply negative magnetic field the system seems to show diamagnetism at low temperature and then makes a very quick drop to paramagnetism. I will attach a graph displaying this. (magnetism on "y axis", temperature on "x") So is this something to be expected or is this and error because I don't have enough scans?