Spin fluctuations in hydrogen-stabilized Laves phase UTi2H5

Abstract

ABSTRACTUranium Laves phase UTi2 does not exist in a pure form, but can be stabilised by the presence of hydrogen, which can be absorbed in concentration exceeding 5 H atoms/f.u. Low temperature specific heat, magnetic susceptibility, and resistivity indicate that UTi2H5 is a spin fluctuator close to the verge of magnetic ordering. Its susceptibility follows at high temperatures the Curie–Weiss law with U effective moment µeff[ = 3.1 µB/U and paramagnetic Curie temperature Θp = −200 K. The temperature dependence of specific heat exhibits a pronounced and weakly field dependent upturn in Cp/T versus T below 10 K reflecting the effect of spin fluctuations. It can be described by an additional T½ term. The Sommerfeld coefficient γ = 256 mJ/mol K2 classifies the compound as a mid-weight heavy fermion. Spin fluctuations are affecting also electrical and thermal transport and thermoelectric power, which all resemble UAl2. A lattice anomaly at ≈ 240 K, attributed to the melting of hydrogen sublattice, reflects in most of bulk properties.