Ferromagnetic cluster spin waves in molecular disks studied by inelastic neutron scattering

Structurally, the two mixed-valence manganese disks Mn${}_{7}$-11 and Mn${}_{7}$-16 differ only in the peripheral ligand but, as a result of a subtle interplay of intramolecular exchange interactions, differ strongly in their magnetic properties, e.g., Mn${}_{7}$-11 possesses a ground-state spin of $S=11$ and Mn${}_{7}$-16 of $S=16$. The exchange interactions in the disks were studied by inelastic neutron scattering. The analysis of the $Q$ dependence of the observed magnetic transition intensities reveals that ferromagnetic cluster spin-wave excitations were observed. In this framework, it was possible to successfully model the experimental data and provide a physical understanding of the magnetism in the two disks.