The low-temperature elementary spin excitations in the AFM molecular wheel Fe${}_{18}$ were studied experimentally by inelastic neutron scattering and theoretically by modern numerical methods, such as dynamical density matrix renormalization group or quantum Monte Carlo techniques, and analytical spin-wave theory calculations. Fe${}_{18}$ involves eighteen spin-5/2 Fe${}^{\mathrm{III}}$ ions with a Hilbert space dimension of $\sim$${10}^{14}$, constituting a physical system that is situated in a region between microscopic and macroscopic. The combined experimental and theoretical approach allowed us to characterize and discuss the magnetic properties of Fe${}_{18}$ in great detail. It is demonstrated that physical concepts such as the rotational-band or $L\mathit{\text{and}}E$-band concepts developed for smaller rings are still applicable. In particular, the higher-lying low-temperature elementary spin excitations in Fe${}_{18}$ or AFM wheels, in general, are of discrete antiferromagnetic spin-wave character.

• Received 27 June 2012

DOI:https://doi.org/10.1103/PhysRevB.86.104403