Onset of magnetism stimulated by H absorption in UNiAl-UFeAl

Abstract

Weak itinerant antiferromagnetism of UNiAl is rapidly suppressed by Fe doping. Magnetic order reappears as weak ferromagnetism in UNi 0.75Fe0.25Al. The onset of magnetism can be shifted by H absorption. UNi0.85Fe0.15Al hydride is an antiferromagnet with TN approx. 70 K. Hydrogenating UNi0.70Fe 0.30Al produces a ferromagnet (TC = 90 K). Here we describe the compound with 20% of Fe and its hydride. The proximity to magnetism shows up as non-Fermi liquid behavior, detected in specific heat as upturn, followed down to 0.3 K, which is gradually suppressed in magnetic fields of several tesla. The hydride was found rather unstable, releasing H at ambient conditions, which made it unsuitable for the specific heat measurement. Magnetization study detected that the hydride shows up as ferromagnet T C ≈ 98 K.