Abstract
We report a study of (0≤x≤0.995 with the nonmagnetic M=Hf, Zr, Sc, Lu, Y, Pr, Ce, Th, and La), with characterization by x-ray diffraction, resistivity, dc susceptibility, and specific heat. Hybridization, and the distance, between the U 5f electrons and the Be s and p electrons is found to control the specific heat γ and therefore the effective mass , while the outer electronic configuration of M plays no role. When the lattice is not expanded by the dopant M, γ (normalized per U mole) reaches a constant value for x>0.15 that is about 40% that of pure . This dilute single-ion behavior is also observed in the resistivity. Surprisingly, the low-temperature magnetic susceptibility (normalized per U mole) is independent of doping for all x. Thus, the large magnetic susceptibility at low temperature in is entirely attributable to single-ion effects. The source of the remaining 60% of the large in and the implications for heavy-fermion superconductivity are discussed.
- Received 27 November 1989
DOI:https://doi.org/10.1103/PhysRevB.41.11073
©1990 American Physical Society