Kagomé antiferromagnets present an ideal construct for studying the unusual physics that result from the placement of magnetically frustrated spins on a low-dimensional lattice. While any two nearest-neighbor spins within the corner-sharing equilateral triangles of the kagomé lattice can couple antiferromagnetically, the third cannot – it is frustrated.

Much interest in preparing model spin-frustrated systems is driven by the potential of such compounds to explain conduction mechanisms in high-T_C cuprate superconductors. Nearly two decades ago, Anderson proposed that the resonating valence bond (RVB) state may explain the scatterless hole transport in doped rare-earth cuprates. The quantum spin liquid phase responsible for RVB is most likely to be found in low-dimensional, low-spin, geometrically frustrated systems. Most theoretical investigations of RVB have focused on S=½ antiferromagnets on kagomé lattices due to their higher degree of geometric frustration relative to triangular lattices. However, a lack of pure kagomé based materials (and most especially those of S=½) has long prevented incisive measurement of their magnetic properties and experimental testing of RVB theory on real spin-frustrated kagomé systems.

Our lab has responded to this need of the condensed matter physics community by making pure materials. We pioneered a redox-based hydrothermal approach for the preparation of large single crystals of jarosites, a mineral family containing kagomé layers comprised of M₃(µ-OH)₃ triangles and based on a KFe₃(OH)₆SO₄ parent. Our accomplishments include continued study of the nature of long-range magnetic ordering in iron jarosites and the synthesis of unprecedented materials featuring structurally perfect S=½ Cu₃(µ-OH)₃ kagomé layers. Our continued efforts now focus on crystal growth of these S=½ systems, the preparation of organic-inorganic hybrid kagomé lattice materials, and charge-carrier doping and the preparation of mixed-valent kagomé systems. Investigation of our unprecedented materials is underway with the group of Young S. Lee of the MIT Physics Department. Studies of stoichiometrically pure spin-frustrated systems will provide critical insight into the behavior of strongly correlated electrons.