Compounds of uranium with the transition metals of the first long period

Detailed Characterization of U–Co Binary Compounds

“…·U 6 Co is a BCS-type superconductor. ·The magnitude of the phonon contribution to the specific heat in U 6 Co is approximately same as that in U 6 Fe. 8) ·The electronic specific coefficient of U 6 Co does not strongly depend on the sample quality; the γ value is 126 mJ/K 2 ·mol.…”

“…These facts suggest that the superconducting behavior might be due to an impurity phase in the UCo crystal. Considering the U-Co binary alloy phase diagram 7) and the similarity of a superconducting transition temperature, we suspected the inclusion of some U 6 Co phase with T c ∼ 2 K. In order to confirm the inclusion of impurity phase, we measured the composition of a single crystal using Co-Kα fluorescence x-ray by EPMA. We clearly observed separated Co-poor domains as shown in Fig.…”

“…With these assumptions, the amount of U 6 Co is estimated to be approximately 7 % by weight. This value is in good agreement with that estimated from EPMA measurements, indicating that the superconducting behavior in UCo is due to a U 6 Co impurity phase.…”

“…UCo 2 is a Pauli-paramagnetic. 1) UCo 5 is a highly anisotropic ferromagnet with T C ∼360 K. 2,3) UCo and U 6 Co have both been reported to be superconducting. 4,5) The early measurements on UCo were made on polycrystalline materials, and a crystal structure without inversion symmetry was proposed based on x-ray powder diffraction.…”

“…Details of the crystallographic parameters and superconductivity in UCo have not been clarified subsequent to this first report. 4,6) In this paper, we report our investigations on the intrinsic physical properties of UCo crystals. We have performed resistivity and specific heat measurements on both a single crystal and a polycrystalline samples of UCo, and checked details of the elemental composition in the crystals by electron probe micro analyses (EPMA).…”