Vortices in Kekulene Molecules

Kekulene is an aromatic hydrocarbon with formula C48H24 arranged in the shape of a closed super-ring as shown in Fig. 2. It consists of a sublattice with 48 C atoms with spin 5/2 and a 24 hydrogen sublattice with spin 2. In this communication, we use Monte Carlo simulations to determine the magnetic structures present in Kekulene for several temperatures (T) and dipole anisotropies ({\delta} = D/J). Our results show that there are two regimes at low temperature separated by a crossover at 2.5 < {\delta}cross < 3.0. For {\delta} < {\delta}cross the ground state has a unique vortex configuration. In the region {\delta} > {\delta}cross arrangements of vortices-antivortices (V-AV) appears. As temperature raises the vortex structure disorders and small oscillations take over. The importance on synthesizing this molecule grounds in the possibility of building real planar structures of sizes at least 10 times smaller than the earlier proposed permalloy nanodots. It is worthy to mention that Kekulene is a planar structure with atomic thickness, which is a great advantage compared with other nanomagnetic structures.