F. Wastin

Advances in the preparation and characterization of transuranium systems

The most remarkable advance that one can report as regards transuranium systems is certainly the discovery of superconductivity above 18 K in PuCoGa5. Motivated by this discovery, we have investigated bulk samples of both PuCoGa5 and its Rh analogue. Characterizations of polycrystalline Co and Rh compounds are reported. The new PuRhGa5 compound is also found to become superconducting above 8 K.

Direct observation of electric-quadrupolar order in UO2

We report direct experimental evidence for long-range antiferro ordering of the electricquadrupole moments on the U ions. Resonant x-ray scattering experiments at the uranium M4 absorption edge show a characteristic dependence in the integrated intensity upon rotation of the crystal around the scattering vector. Although quadrupolar order in uranium dioxide was advocated already in the 1960s no experimental evidence for this phenomenon was provided until now. We conclude with a possible model to explain the phase diagram of the solid solutions of UO2 and NpO2. We suggest that in the region 0.30 < x < 0.75 neither the transverse nor the longitudinal quadrupole ordering can dominate, leading to frustration and only short-range ordering.

Progress on solid compounds of actinides

Abstract The preparation of solid actinide compounds at the European Institute for Transuranium Elements covers topics from metal refining to the synthesis and characterization of new materials in single-crystal form. A review of techniques used in the preparation chemistry of transuranium elements is presented. Reliable and sensitive characterization techniques have been developed to yield a good description of the quality of the samples. It is important that the characterization includes more than chemical (impurities, traces, etc.) and metallurgical (defects, inclusions, composition, crystal structure, etc.) analyses but also initial physical properties. We report our progress in the study of families of compounds such as pnictides, chalcogenides and binary and ternary intermetallic compounds.

New actinide ternary intermetallic compounds: synthesis, characterization and physical properties

Abstract Twelve new ternary intermetallic compounds of light actinide elements from Th to Pu, namely U 4 Tc 7 Si 6 , U 4 Tc 7 Ge 6 , Np 4 Ru 7 Ge 6 , U 2 Tc 3 Si 5 , Np 2 Re 3 Si 5 , Pu 2 Re 3 Si 5 , Th 2 Mo 3 Si 4 , U 2 Mo 3 Si 4 , U 2 Mo 3 Ge 4 , Np 2 Mo 3 Si 4 , Np 2 Mo 3 Ge 4 , and Pu 2 Mo 3 Si 4 , were obtained. The structures of these compounds are discussed as well as some preliminary physical property studies. Magnetic susceptibility measurements show that An 2 Mo 3 (Si or Ge) 4 compounds are paramagnetic at all temperatures studied and that U 4 Tc 7 Si 6 orders antiferromagnetically around 25 K. Mossbauer spectroscopy on Np 4 Ru 7 Ge 6 does not show a magnetic splitting down to 4.2 K.

Possible pairing mechanisms of PuCoGa5 superconductor

We examine possible pairing mechanisms of superconductivity in PuCoGa

Magnetic properties of NpNiSi2

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Determination of the Antiferroquadrupolar Order Parameters in UPd3

based on spin-fluctuations or phonons as mediating bosons. We consider experimental data of specific heat C(T) and resistivity

Variability of 5f states in plutonium carbides

\rho(T)

Synthesis and electronic properties of Th-N films

as input to determine a consistent scattering boson with the superconducting transition temperature of 18.5K in PuCoGa

Magnetic and electronic properties of NpRhGe

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