Electron-spectroscopy study of rare-earth trihalides

We have studied the electronic structures of rare-earth trihalides ${\mathrm{LaF}}_3$, ${\mathrm{LaCl}}_3$, ${\mathrm{CeF}}_3$, ${\mathrm{CeCl}}_3$, and ${\mathrm{GdF}}_3$ by x-ray photoemission spectroscopy (XPS), 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 model as being due to the charge transfer from the ligand 2p level to the rare-earth unfilled 4f level. The parameters obtained from fitting these core-level spectra using the Gunnarsson-Schönhammer-model approach are consistent with the valence-band XPS and the conduction-band BIS spectra. In the higher binding-energy side (10–40 eV) of 3d XPS, several more satellites are observed. Through comparing with other core-level XPS and EELS, we find that they are mainly loss structures arising from the interband transition, the rare-earth 5p excitation, and the charge-transfer transition, but there are some contributions from the ‘‘intrinsic’’ plasmon excitations as well.