Discrete antiferromagnetic spin-wave excitations in the giant ferric wheel Fe18

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-III ions with a Hilbert space dimension of similar to 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 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.