Vacuum Ultraviolet Reflectance Spectra and Band Structures of Pyrites (FeS2, CoS2 and NiS2) and NiO Measured with Synchrotron Radiation

Reflectance spectra of FeS 2 , CoS 2 and NiS 2 pyrites have been measured in the photon energy region from 4 to 30 eV with synchrotron radiation and compared with the results of NiO and related compounds. Dielectric constants, optical constants, effective electron numbers as well as energy-loss functions are evaluated by means of the Kramers-Kronig analysis. Fine structures of the reflectance spectra are qualitatively interpreted providing information on band structures. Characteristic features of band structures related to the 3 d electrons in the low-spin state are experimentally elucidated.