Anomalous transport properties of heavily doped polycrystalline La0.825Sr0.175Mn1-xCuxO3

heavily doped single-phase polycrystalline La0.825Sr0.175Mn1-xCuxO3 (0.20 less than or equal to x less than or equal to 0.40) has been pre pared. Above paramagnet to cluster-spin-glass transition temperature, the electron spin resonance measurement suggests that there exist ferromagnetic clusters in the paramagnetic background. For the transport properties, within the range of compositions of x less than or equal to 0.32, the resistivity (rho) displays Mott's variable-range hopping insulating behavior and increases with the increase of Cu content. But at the doping level 1/3 less than or equal to x, it is surprising that rho is several orders of magnitude smaller than that of samples x less than or equal to 0.32 and in the range 1/3 less than or equal to x less than or equal to 0.40, rho decreases with increasing x. It is suggested that two different kinds of conduction mechanism coexist in this ABO(3) structure oxide.