We report the magnetic properties of a new class of materials: ${\mathrm{Ni}}_9$${\mathrm{Te}}_6^{\mathit{n}+}$ and ${\mathrm{Co}}_6$${\mathrm{Te}}_8^{\mathit{n}+}$ with n=0, 1, 2. These cluster compounds, which can be charged by chemical means from neutral to 2+, provide a unique and novel way to change the Fermi level. For most charge states we observe quenching of the spin and orbital moments at low temperatures, accompanied by a large value for the temperature independent susceptibility of the ground state. The generic presence of low-energy magnetic excitations in these compounds indicates that these systems exhibit strong electron correlations and form mesoscopic analogs of the mixed-valence–heavy-fermion compounds.

• Received 22 December 1992

DOI:https://doi.org/10.1103/PhysRevLett.71.1768