Optical Properties of GdS,GdSe,GdTeamd LaS

The reflectivity of single crystals of Gd chalcogenides and of LaS has been measured at room temperature in the spectral region from 40 μm to 12 eV. The reflectivity data have been analyzed in terms of the optical constants by means of the Kramers‐Kronig relation. The dielectric function has been decomposed into contributions of free and bound electrons. Hence the plasma resonance of the conduction electrons and their effective mass have been determined. The position in energy of the 4f level in GdS has been found at 9 eV below EF by comparing the interband transitions of GdS and LaS . The stronger damping of the conduction electrons of GdS compared to LaS suggests the presence of a spin‐disorder scattering in GdS already at 300 K.