حسین رعنایی

In this article, the effect of geometrical shape as well as initially magnetization on magnetization reversal of a Permalloy magnetic nanoring has been investigated by using micromagnetic simulations. The simulations were performed using object oriented-micromagnetic framework software (OOMMF). The magnetic nanoparticles are divided into nanoscale cells to calculate the magnetic dynamic behavior governed by the Landau- Lifshitz- Gilbert equation. The hysteresis loop of whole magnetic system is achieved by these numerical calculations. In the previous work the geometrical effect of a magnetic nanoring has been studied while the magnetic system initialized at random anisotropy. The possibilities of transition of magnetic state from vortex to onion states as well as the mobility of domain wall in the rings are investigated by altering the ring linewidth while the system is initially magnetized. In these nanoparticles, the magnetization reversal depends strongly on ring linewidth. The onion state is a dominant state in the reversal process and the coercive field is also affected by these states and particularly the pinned domain wall. These features can be understood by considering the competition between exchange and magnetostatic energy stems from demagnetization field. The domain wall motion of a narrow nanoring was found to be much sensitive by altering the field as compared to the thicker nanoring.