Superconducting phase transitions in the milikelvin temperature range in splat-cooled U-Pt alloys*

M Chrobak, Z Tarnawski, S Sowa, M Krupska, N-T H Kim-Ngan, M Paukov, V Buturlim and L Havela

Abstract

We present the temperature and magnetic-field dependence of electrical resistivity (ρ(T, B) dependence) in the milikelvin range for U-Pt alloys with Pt concentration in the range of 0–15 atomic percent (at.%) prepared by splat-cooling technique. The high-temperature cubic γ-U phase can be stabilized down to room temperature in the samples with 15 at.% Pt. All samples exhibit superconducting transitions below 1.1 K revealed by abrupt resistivity drops with transition widths of several tens of milikelvins in zero magnetic field. The H–T diagrams for all investigated alloys are in good agreement with the Ginzburg-Landau approximation. The U-Pt alloys with cubic γ-U phase are very stable in air and hydrogen exposure at atmospheric conditions. They can absorb a large amount of hydrogen upon applying hydrogen pressure  >2.5 bars and easily release it by heating in vacuum, showing the possibility of using U-Pt-based hydrides as a medium for hydrogen storage