Effect of deuterium absorption on the heavy-fermion compound UPdIn

Abstract

The heavy fermion compound UPdIn is found to absorb deuterium without disproportionation to yield UPdInD_0.7. Magnetization, heat capacity, x-ray, and neutron-diffraction measurements have been carried out to probe the structural and magnetic properties of this deuteride. It is found that deuterium absorption results in a highly anisotropic lattice expansion, without changing the Fe₂P-type hexagonal structure of the parent compound. The magnetic ordering temperature is enhanced to 80 Κ and the low-temperature uranium moment to 2.5μ_B from their corresponding values of 21 K and 1.5μ_B, respectively, in the parent compound. Neutron-diffraction studies on the deuteride reveal antiferromagnetic ordering of the uranium moments and doubling of unit cell along the c axis. Heat capacity measurements show a large reduction in the value of electronic specific heat coefficient γ from 260 mJ mol^-1 K^-2 in UPdIn to 30 mJ mol^-1 K^-2 in UPdInD_0.7, indicating a significant reduction in the hybridization between uranium 5f electrons and those on the surrounding atoms.