VORTEX STRUCTURES IN CYLINDRICAL MAGNETIC NANOPARTICLES

Abstract

In this chapter we present a theoretical study of magnetic ground states, domain walls and magnetization reversal process in nanomagnets with cylindrical symmetry. It is well known that macroscopic ferromagnets are organized in domains, and nearest domains are separated by domain walls, whose typical sizes are comparable with the dimensions of typical magnetic nanostructures. On the other hand, when the dimensions of a nanomagnet are in the range of the exchange length of the magnetic material, we can expect a single-domain behavior. As particle size increases, dipolar interactions become more and more important, and the magnetic ground states start deviating from single domain, forming magnetic structures like vortex, flower, leaf and onion states as a function of their geometry. These magnetic states are the result of competition between exchange coupling, dipolar interactions, and anisotropy. We also present current research on magnetization reversal processes in nanodots and nanotubes, where we show that vortex-like structures play a crucial role in the magnetic switching of ferromagnetic nanoparticles.