The study of magnetic phase transitions in insulating molecular solids provides new insights into mechanisms of magnetic coupling in the solid state and into critical phenomena associated with these transitions. Only a few such materials are known to display cooperative magnetic properties. The use of high-spin molecular components would enhance intermolecular spin-spin interactions and thus a series of charge-transfer (CT) salts have been synthesized that utilize the spin S = 1 molecular cation, [Mn(C5(CH3)5)2]+ (decamethylmanganocenium). The structure and cooperative magnetic behavior of [Mn(C5(CH3)5)2] +[TCNQ]- (decamethylmanganocenium 7,7,8,8-tetracyano-p-quinodimethanide) are reported. This salt is a bulk molecular ferromagnet with the highest critical (Curie) temperature (Tc = 6.2 K) and coercive field (3.6 × 103 gauss), yet reported for such a material.
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