  The emergence of complex electronic behaviour from simple ingredients has
resulted in the discovery of numerous states of matter. Many examples are found
in systems exhibiting geometric magnetic frustration, which prevents
simultaneous satisfaction of all magnetic interactions. This frustration gives
rise to complex magnetic properties such as chiral spin structures
orbitally-driven magnetism, spin-ice behavior exhibiting Dirac strings with
magnetic monopoles, valence bond solids, and spin liquids. Here we report the
synthesis and characterization of LiZn2Mo3O8, a geometrically frustrated
antiferromagnet in which the magnetic moments are localized on small transition
metal clusters rather than individual ions. By doing so, first order
Jahn-Teller instabilities and orbital ordering are prevented, allowing the
strongly interacting magnetic clusters in LiZn2Mo3O8 to probably give rise to
an exotic condensed valence-bond ground state reminiscent of the proposed
resonating valence bond state. Our results also link magnetism on clusters to
geometric magnetic frustration in extended solids, demonstrating a new approach
for unparalleled chemical control and tunability in the search for collective,
emergent electronic states of matter.
