We have observed giant magnetic moments in clusters of rhodium, ${\mathrm{Rh}}_{\mathit{n}}$(n=12–32), consistent with ferromagnetic ordering of the 4d electrons. Ferromagnetic behavior has not been reported previously in pure 4d transition metals. Rhodium clusters are superparamagnetic at 93 K, with magnetic moments of between 0.3 and 1.1${\mathrm{\mu }}_{\mathit{B}}$ per atom. We find that ${\mathrm{Rh}}_{15}$, ${\mathrm{Rh}}_{16}$, and ${\mathrm{Rh}}_{19}$ have magnetic moments per atom that are significantly larger than those of adjacent cluster sizes.

• Received 2 April 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.923