Effect of deuterium absorption on the heavy-fermion compound UPdIn

The heavy fermion compound UPdIn is found to absorb deuterium without disproportionation to yield ${\mathrm{UPdInD}}_{0.7}.$ 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 ${\mathrm{Fe}}_2\mathrm{P}$-type hexagonal structure of the parent compound. The magnetic ordering temperature is enhanced to 80 K and the low-temperature uranium moment to $2.5{\mu }_B$ from their corresponding values of 21 K and $1.5{\mu }_B,$ 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 ${\mathrm{mol}}^{\mathrm{-}1}$ ${\mathrm{K}}^{\mathrm{-}2}$ in UPdIn to 30 mJ ${\mathrm{mol}}^{\mathrm{-}1}$ ${\mathrm{K}}^{\mathrm{-}2}$ in ${\mathrm{UPdInD}}_{0.7},$ indicating a significant reduction in the hybridization between uranium $5f$ electrons and those on the surrounding atoms.