ELECTRON PROPERTIES AND SURFACE EFFECTS OF RARE-EARTH SYSTEMS

Recent experimental results concerning the surface-related electronic structure of rare-earth solids are presented. Special attention is pai d to the occurrence of surface-valence transitions in trivalent or mix ed-valent compounds of Sm, Eu, Tm, and Yb that are due to energeticall y lowering of unoccupied 4f-states caused by the reduced atomic coordi nation at the surface. Similar phenomena are encountered in Ce-systems leading to a decrease of 4f-hybridization in the outermost atomic sur face layer. The importance of this phenomenon for the correct interpre tation of electron-spectroscopic data of Ce-systems is discussed. Expe rimental evidence for transitions from a localized to an itinerant beh avior of the 4f-states is obtained for CeRh3.