| The properties of UCoGe and URu2Si2 have been investigated by substitution of Ni into the Co site and Fe and Os into the Ru site. Polycrystalline samples of UCo1-xNi xGe (0 ≤ x ≤ 1), URu2- xFexSi2 (0 ≤ x ≤ 2), and URu2-xOs xSi2 (0 ≤ x ≤ 1.2) were prepared by arc-melting and studied by x-ray diffraction, energy dispersive x-ray spectroscopy, electrical resistivity, specific heat, and magnetization measurements. In the UCo1-xNixGe system, the material evolves from the ferromagnetic state to the antiferromagnetic state with increasing Ni concentration. The superconducting state is destroyed by small amounts of Ni substitution and does not appear to re-emerge in any other portion of the phase diagram. Measurements on URu2- xFexSi 2 reveal a two-fold enhancement of the "hidden order" (HO)/large moment antiferromagnetic (LMAFM) phase boundary T0( x). The T0(P ch ) curve, obtained by converting x to "chemical pressure" Pch , is strikingly similar to the T0(P) curve, where P is applied pressure, for URu2Si2---both exhibit a "kink" at 1.5 GPa and a maximum at ∼ 7 GPa. This similarity suggests that the HO-LMAFM transition at 1.5 GPa in URu2Si 2 occurs at x ≈ 0.2 (Pch ≈ 1.5 GPa) in URu2-xFe xSi2. The transition temperature in URu2- xOsxSi 2 is enhanced from 17.5 K at x = 0 to 50 K at x = 1. At x ≈ 0.2, the samples seem to evolve to another ordered phase as indicated by the decreasing size of the HO gap. |
