ANOMALOUS CHARGE-TRANSPORT PHENOMENA IN MOLECULAR-BASED MAGNET V(TCNE)X.Y(SOLVENT)

We present charge transport studies on recently developed molecular-ba sed magnets V(TCNE)x . y(solvent) (TCNE = tetracyanoethylene) which sh ow local magnetic ordering at temperatures, T, as high as 400 K. V(TCN E)x . y(solvent) prepared from the solvent CH2Cl2 has sigma(300 K) app roximately 10(-3) S/CM, and that prepared from the solvent CH3CN has s igma(300 K) approximately 10(-5) S/cm. The sigma(T) of both materials follows the Mott 3D variable range hopping [log(T1/2sigma) is-proporti onal-to T-1/4] behavior. An anomalously strong T-dependent ac conducti vity is likely caused by the short-range ferrimagnetic correlations. C ole-Cole analysis of the ac complex dielectric constant suggests there are two relaxation mechanisms, with an Arrhenius relation fitted to b oth. The microwave frequency response is consistent with audio frequen cy data and yields a localization length of approximately 5 angstrom, comparable with the dimensions of a [TCNE]-. group.