Electrical transport and magnetic properties of misfit layered compounds intercalated with cobaltocene

The electrical and magnetic properties of misfit layered cobaltocene comple xes of composition (PbS)(1.18)(TiS2)(2)(CoCp2)(0.28), (PbS)(1.14)(TaS2)(2)( CoCp2)(0.28), and (PbSe)(1.12)(NbSe2)(2)(CoCp2)(0.27) [Cp = C5H5-] were inv estigated. All the pristine chalcogenides studied exhibit a metallic behavi or and a magnetic susceptibility virtually independent of temperature. More over, the Ta and Nb compounds-the later impurified with NbSe2-undergo a sup erconducting transition at low temperatures (T-C < 4 K). Upon cobaltocene i ntercalation, the Ta and Nb systems behave similarly. The superconducting t ransition temperature changes very little and the metallic behavior is pres erved: the susceptibility is temperature-independent, whereas the resistivi ty increases with increasing temperature. This is consistent with an electr on transfer from the metallocene to the host. The Ti intercalate behaves ma rkedly differently. Thus, the complex undergoes a metal semiconducting tran sition below 70 K, and the magnetic data are significantly temperature-depe ndent. This localized moment may be consistent with the minimum observed in the resistivity values. The good overlapping properties 4d and 5d orbitals relative to 3d orbitals may account for the delocalization of the electron donated by the guest to the conduction band of the host.