OPTICAL AND PHOTOELECTRICAL STUDIES OF ELECTRONIC-STRUCTURE OF R(3)AU(3)SB(4) (R=LA,CE AND PR)

The electronic structures of a magnetic semiconductor Ce3Au3Sb4 and th e related materials, La3Au3Sb4 and Pr3Au3Sb4, have been investigated b y reflectivity and resonant photoemission spectra. From the resonant p hotoemission spectra of Ce3Au3Sb4, the hybridization between the Ce4f state and the Sb5p valence band was found to be weak. This result is c onsistent with the electronic structure which is derived from the anal ysis of the optical data about the energy gap. The experimentally dete rmined Electronic structure is compared with a band calculation of La3 Au3Sb4. The unoccupied 4f state is concluded to be about 3 eV above th e Fermi level, which is higher by 2 eV than the result of the band cal culation. The exciton like absorption due to the transition from 4f to 5d states was observed. The intra-atomic Coulomb interaction between 4f and 5d states is thought to play an important role.