The size effects of the magnetic properties for the 200-nm Co nanorings: Monte Carlo simulation

In this work, using Monte Carlo simulation, we study the magnetic properties of individual Co nanorings with the outer diameter of 200 nm, the thickness of 10 nm, 20 nm, 30 nm and the varying width from 10 nm to 90 nm, obtaining various spin configurations. The simulated results indicate that, there exist evident size effects on the magnetic states and magnetization processes of the nanorings; in the magnetization reversal process there exist the onion-type state for the narrow rings, and the vortex-type state and onion-type state for the wide rings, respectively. The vortex-type spin configuration is responded for the step of hysteresis loops, which is named as the second stable state. At the same time, it is found that the stability of the second stable state has evident size effect. Moreover, the simulated results are consistent with experimental facts.