W.W. Kim

Specific heat measurement on UAl4

Abstract UAl 4 is one of the few binary compounds for which published data on specific heat measurements do not yet exist. We have filled this gap for the temperature range from 1.5 to 12 K. The determined value of the Sommerfeld constant γ is 46 mJ mol −1 K −2 ; the Debye temperature Θ D is 360 K. The measured sample was prepared in an arc melter, annealed and X-ray tested for phase purity. Measurements of susceptibility and magnetization vs . field were also made.

Hybridization and its influence on the electronic properties of UA12

Abstract Doping experiments in UA1 2− x M x , with MGa, Si or Mn, have been carried out, and the single-phase samples were characterized by magnetic susceptibility, χ, and low temperature specific heat, C . The parameter important for the relatively large γ and the T 3 ln T spin fluctuation term in the specific heat appears to be the interatomic spacing rather than either coherence on the Al sublattice or the particular electronic character of the dopant atom.

Formation of Kondo clouds in U(Sn1−xMx)3 compounds (M = Al, Ga, Ge)

Abstract USn3 has an unusually high γ value of 169 mJ mole−1 K−2 in comparison with its neighboring compounds UAl3, UGa3, USi3, and UGe3. To study the formation of this high γ value we prepared pseudobinary U(Sn1−xMx)3 compounds (M = Al, Ga, Si, Ge, and x = 0, 0.1, 0.25, 0.5). From X-ray diffraction, specific-heat and susceptibility measurements we conclude that the high γ value is not only due to f-ligand hybridization, but also to the formation of Kondo clouds (40%).

Superconducting and magnetic properties of Y1−xUxRh4B4

Abstract The heat capacity, magnetic susceptibility and magnetization of Y 1− x U x Rh 4 B 4 were determined within the range from x = 0 to x = 0.65. The influence of the local magnetic moments of the U atoms (d U-U = 5.27 A ) in the CeCo 4 B 4 structure of the tetragonal RERh 4 B 4 was studied. A.c. susceptibility measurements showed a rather large value for the T c depression of d T c /d x = −1.88 K per at. % U in the lower concentration range x = 0.0 to x = 0.06. In comparison with the (Bardeen-Cooper-Schrieffer) BCS theory and the Abrikosov-Gorkov model for dilute magnetic impurities, the decrease in the jump in specific heat at T c vs. the depression of T c is rather strong in these samples, so the existence of a demagnetizing Kondo cloud around the U moments seems likely. In the samples containing more U, the magnetization and d.c. susceptibility showed a tendency towards magnetic behaviour, but no evidence for long-range magnetic order was found.