As part of my project, i have to calculate the coercive fields of a circular disc of 50nm and 100 diameter with 4nm thickness each and compare them. I used a micromagnetic simulation software called Nmag to simulate them. As far as i know, i have done the simulation part perfectly. The problem here is, the coercive field increases when the diameter is made smaller. I couldn't find any difference between 100nm, 150nm and 200 nm diameters. But when it comes to 50nm the coercive field increases. So i guess this should be more efficient as thinner magnets can be used and still more field has to be applied to flip the magnetic moment. Can someone please explain how the coercive field changes with the size? Were my results correct?