How Does the Ising Model Exhibit Diamagnetism to Paramagnetism Transition in 2D?

[Heimisson]

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?

 

[Nate810]

It is expected to see a transition from diamagnetism to paramagnetism when applying an external magnetic field. This transition typically occurs when the temperature drops below a certain critical temperature, which can vary depending on the strength of the external magnetic field. It is possible that you are not seeing this transition because your scans do not reflect the full range of temperatures over which the transition would occur. It is also possible that the transition is occurring but is not visible in your graph due to insufficient data points or other factors.