Incoherent metallic state in a double-exchange ferromagnet: transport and optical properties of La1−xSrxMnO3

Transport and optical studies on La0.825Sr0.175MnO3 indicate that the charge dynamics undergoes a coherent–incoherent crossover at a certain critical region of the dc conductivity. The present result suggests that the ferromagnetic metallic phase below the Curie temperature TC is divided into two regions, a “high-temperature incoherent” metallic and a “low-temperature coherent” metallic region. “Colossal magnetoresistance” is a characteristic of the former region.