Soft X-ray Absorption Spectra of Uranium Intermetallics: Fid-Bau Portal

Soft X-ray Absorption Spectra of Uranium Intermetallics

Sarma, D. D. / Krumrnacher, S. / Hillebrecht, F. U. / Gudat, W.

Abstract The hybridization of highly correlated f electrons in lanthanides and actinides with the extended band states is known to give rise to many interesting electronic and magnetic properties , manifesting a competition between nearly localized and more delocalized behaviour of the f electrons. Recently there has been a rapid increase in the interest due to the discovery of heavy fermions in this class of compounds . In the case of Ce compounds, the difference in the 4f hybridization have been usefully studied by x-ray absorption spectroscopy (XAS)3,4. However, very few studies5−7 have been performed on uranium compounds using XAS. Due to the present interest in understanding the nature of f states in uranium intermetallics, we have studied several of these at d → f absorption regions (4d and 5d thresholds) employing soft x-ray absorption in the total yield technique. The compounds were so chosen as to represent the wide variety of electronic and magnetic properties found in uranium intermetallics. Thus we have studied UPd3 , UCu5 (antiferromagnetic), UNi5 (Pauli paramagnetic), UCo5.5(ferromagneticj and UxV1−xB4 (Pauli to ferromagnetic as a function of x). Moreover UPd3 is believed to have a localized f2 configuration, whereas the other compounds are believed to exhibit correlated band-like behaviour with f-occupancy∼2.5−2.8.