Micromagnetic simulation of iron nanorings

We performed a systematic study of the magnetic properties of iron nanorings with 80 nm external diameter varying the thickness in the framework of micromagnetic theory. Hysteresis loops were determined in an applied magnetic field ranging from −800 to 800 mT. The behavior of coercive field as a function of the ratio of the inner din to the outer dout diameter (0.1-0.9) and the thickness (t=20-200nm) are presented. The evolution of the magnetization spin configuration is shown for different switching magnetic fields. We found large coercive fields for din/dout>0.5 and t=160-200nm due to the absence of the vortex states and the presence of out-plane and in-plane spin configurations.