Regensburg 2000 – wissenschaftliches Programm
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AM: Magnetismus
AM 19: Spektroskopie I
AM 19.1: Hauptvortrag
Donnerstag, 30. März 2000, 09:30–10:00, H22
5f-electron localization in PuSe and PuSb — •Ladislav HAVELA1 and Thomas GOUDER2 — 1Department of Electronic Structures, Charles University, Ke Karlovu 5, 121 16 Prague 2, Czech Rep. — 2European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe
Thin layers technique is a convenient way to suppress a surface O segregation, which has been preventing until now any high-temperature photoemission study in actinide materials. Here we describe results obtained on thin layers of PuSb and PuSe, studied by XPS and and high-resolution UPS. Valence band spectra show localization of the 5f-states and a low density of states at the Fermi level in PuSb, which is a 5f-ferromagnet (Tc = 85 K). In PuSe, which can be classified as a heavy fermion system with low carrier density, we observed besides such emission from the localized 5f states three additional narrow peaks in the valence band (at 0.85 eV and 0.50 eV binding energy, and at the Fermi level), related to the 5f emission, as well. These features are very sensitive to stoichiometry deviations and disappear for PuSe prepared at T = 77 K, exhibiting spectra similar to PuSb. The temperature dependence study (77 - 673 K) demonstrates that the intensity of all three peaks decreases with increasing T, which can be tentatively attributed to many-body effects. Similar information is obtained from the 4f core-level spectra, showing also an unusual temperature dependence.