Y. Sawaki

Optical reflectivity spectra measured on cleaved surfaces of La1-xSrxMnO3 : Evidence against extremely small Drude weight

Optical reflectivity spectra were measured on cleaved surfaces of La 1- x Sr x MnO 3 single crystals (0≤ x ≤0.30). The optical conductivity σ(ω) shows, keeping single-component nature, an incoheren...

Optical Reflectivity Study on Al-Substituted La0.825Sr0.175MnO3: Unconventional Localization State Induced by Vacancies in the Ferromagnetic Kondo Lattice

Al-substituted La 0.825 Sr 0.175 MnO 3 shows a resistance minimum at low temperature. However, this cannot be explained within a simple localization picture because the optical conductivity is characterized not only by a non-Drude infrared peak but also by an additional absorption at about 3 eV. A small amount (∼3%) of vacancy (Al impurity) in the ferromagnetic Kondo lattice changes the overall character of the charge dynamics and induces the unconventional localization state.

Optical reflectivity study on magnetoresistive manganese perovskites: impurity effect on the ferromagnetic–metallic and charge-ordered states

Abstract Impurity effect on manganese perovskites are investigated by the optical reflectivity measured on cleaved surfaces of the single crystals. The Al impurity affects optical conductivity σ ( ω ) of ferromagnetic–metallic La 1− x Sr x MnO 3 over a wide energy range up to 1 eV or higher, contrary to the simple-Drude picture. The energy gap of the charge-ordered (CO) state in Nd 0.5 Sr 0.5 MnO 3 is about 0.5 eV , much larger than that suggested by the previous studies using polished surfaces. This indicates that the CO state can be easily damaged by external disorder.

Optical Spectra Measured on Cleaved Surfaces of Double-Exchange Ferromagnet La1—xSrxMnO3

Optical reflectivity spectra were measured on cleaved surfaces of La1-xSrxMnO3 single crystals (x=0.175, T_C=283 K) over a temperature range 10-295 K. The optical conductivity

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

sigma(\omega)

Al-substitution effect on charge transport in La 1 − x Sr x MnO 3 : Incoherent metallic state in a double-exchange ferromagnet

shows, keeping single-component nature, incoherent-to-coherent crossover with increase of electrical conductivity. The

Effect of oxygen annealing on the electrical properties ofLa1−xSrxMnO3+δsingle crystals around the compositional metal-insulator transition

\sigma(\omega)

Electronic structure of the double-exchange ferromagnetLa0.825Sr0.175MnO3studied by optical reflectivity

spectrum of low-temperature ferromagnetic-metallic phase (10 K) exhibits a pronounced Drude-like component with large spectral weight, contrary to the previous result. The present result indicates that the optical spectrum of the manganites is sensitive to condition of sample surfaces.

Incoherent-to-coherent crossover of optical spectra in La 0.825 Sr 0.175 MnO 3 : Temperature-dependent reflectivity spectra measured on cleaved surfaces

Abstract 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.