Temperature-dependent optical reflectivity spectra measured on cleaved surfaces of La 1− xSr xMnO 3

Abstract

Optical reflectivity spectra were measured on cleaved surfaces of La 0.825Sr 0.175MnO 3 single crystals ( T C=283 K) over a temperature range 10–295 K. The optical conductivity σ( ω) shows incoherent-to-coherent crossover with decreasing temperature. The present result suggests that there are two types of the ferromagnetic-metallic phase below T C – a “high-temperature incoherent” metallic (HIM) and a “low-temperature coherent” metallic (LCM) phase. “Colossal magnetoresistance” (CMR) is a characteristic of the HIM phase.