Optical properties of FeAs-based parent compound: A comparative study for polycrystalline EuFe2As2 and LaFeAsO

We report on a comparative optical investigation on EuFe₂As₂ and LaFeAsO polycrystalline samples. The spin-density wave (SDW) partial gap is observed for both compounds. The gap-like absorption peaks in the real part of conductivity for EuFe₂As₂ and LaFeAsO scale with their respective T _SDW. Most remarkably, the study reveals a substantial difference in optical reflectance spectra for the two prototype compounds of 122 and 1111 systems: EuFe₂As₂ shows a much higher reflectivity with fewer phonon modes than that of LaFeAsO. This yields optical evidence for much stronger anisotropy between ab-plane and c-axis in 1111-type compounds.