Superconductivity in the splat-cooled UMo alloys*

N-T H Kim-Ngan, S Sowa, M Krupska, M Paukov, I Tkach and L Havela

Abstract

We have investigated the superconductivity in splat-cooled UMo alloys by low-temperature resistivity and specific-heat measurements down to 0.4 K. The γ-U materials, such as U-Mo15 (with 15 at.% Mo doping), exhibit a conventional BCS superconductivity with T_c = 2.1 K and upper critical field exceeding 5 T, much higher than that for α-U materials. The alloys with <10 at.% Mo doping consist of a mixed γ + α-U phase. The superconducting transition in the U-Mo6 revealed by a smooth decrease below 1.5 K and a sharp drop at 0.6 K in the resistivity indicating that γ-U grains are embedded in the α-U matrix. The superconductivity transition was revealed by λ-type peak at T_c in the C(T) curve only for U-Mo15, while only one broad peak at T_c in the C(T) curves were observed for other UMo splats. With applying the magnetic fields, the resistivity jumps and specific-heat peaks move to lower temperatures