Inelastic neutron scattering has been applied to the study of the spin dynamics of Cr-based antiferromagnetic octanuclear rings where a finite total spin of the ground state is obtained by substituting one ${\mathrm{Cr}}^{3+}$ ion $(s=3∕2)$ with $\mathrm{Zn}(s=0)$, $\mathrm{Mn}(s=5∕2)$, or $\mathrm{Ni}(s=1)$ dications. Energy and intensity measurements for several intramultiplet and intermultiplet magnetic excitations allow us to determine the spin wave functions of the investigated clusters. Effects due to the mixing of different spin multiplets have been considered. Such effects proved to be important to correctly reproduce the energy and intensity of magnetic excitations in the neutron spectra. On the contrary to what is observed for the parent homonuclear ${\mathrm{Cr}}_8$ ring, the symmetry of the first excited spin states is such that anticrossing conditions with the ground state can be realized in the presence of an external magnetic field. Heterometallic ${\mathrm{Cr}}_{7}M$ wheels are therefore good candidates for macroscopic observations of quantum effects.

• Received 29 September 2004

DOI:https://doi.org/10.1103/PhysRevB.71.174407