ELECTRON-SPECTROSCOPY STUDY OF RARE-EARTH TRIHALIDES

We have studied the electronic structures of rare-earth trihalides LaF 3, LaCl3, CeF3, CeCl3, and GdF3 by x-ray photoemission spectroscopy (X PS),bremsstrahlung isochromat spectroscopy (BIS), and electron-energy- loss spectroscopy (EELS). The double peak structures of the rare-earth 3d core-level XPS can be understood within the;Anderson impurity mode l as being due to the charge transfer from the ligand 2p level to the rare-earth unfilled 4f level. The parameters obtained from fitting the se core-level spectra using the Gunnarsson-Schonhammer-model approach are consistent with the valence-band XPS and the conduction-band BIS s pectra. In the higher binding-energy side (10-40 eV) of:3d XPS, severa l more satellites are observed. Through comparing with other core-leve l XPS and EELS, wi find that they are mainly loss structures arising f rom the interband transition, the rare-earth 5p excitation, and the ch arge-transfer transition, but there are some contributions from the '' intrinsic'' plasmon excitations as well.