Properties of molecular-based frustrated magnets

The magnetic properties of cobalt complexes of BTCA (BTCA = 1,3,5 benzenetricarboxylic acid) have been investigated. The trianion of the BTCA ligand has the ability to create lattices with competing interactions leading to frustration. A dodecahydrate phase, Co(3)BTCA(2)(H2O)(12), is obtained from room temperature aqueous solutions and consists of pendant chains with very small interactions. Varying the reaction conditions leads to an amorphous phase which displays many of the features of a spin glass: hysteresis, remanent magnetization, frequency dependent susceptibility, aging effects, and an inverse field dependence of the de susceptibility. The dehydration state and corresponding magnetic properties are strongly dependent on the temperature of the original reaction. Reaction temperatures below 78 degrees C lead to the pendant chain while temperatures greater than 78 degrees C yield more interesting glassy phases. These phases exhibit many properties of reentrant spin glasses.