Stabilization of the in-plane vortex state in two-dimensional circular nanorings

We study two-dimensional circular nanorings composed of elementary magnetic moments arranged in sites of a square lattice. Using a microscopic approach that takes into account the dipolar and nearest-neighbor exchange interactions, we calculate the spin-wave frequencies and profiles to draw conclusions regarding the stability of the assumed magnetic configuration. We show that, in contrast to square rings, in circular rings the exchange-driven reorientation is sensitive to both the external and internal sizes of the ring. We associate this behavior with the delocalized character of the lowest spin-wave excitation, and show that, consequently, the in-plane vortex state can be stabilized even in the case of strong exchange interactions. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794004]