Impact of hydrogen absorption on crystal structure and magnetic properties of RE2T2X compounds

Abstract

RE2Pd2In, RE2Pd2Sn compounds (RE=rare earth) absorb, depending on the rare earth (RE) element, different amounts of hydrogen. The parent compounds RE2Pd2In show the linear decrease of both lattice parameters and the unit cell volume with the increasing atomic number of RE, attributed to the lanthanide contraction. All the compounds absorb at least 2H/f.u.; the tetragonal structure is merely expanded. The expansion is anisotropic (Δc/c>Δa/a), and for RE=Tb, Dy, Ho, and Er the lattice even contracts along the a-axis (Δa/a<0), whereas Δc/c still weakly increases. A higher H concentration can be achieved in the compounds with light rare earths (La, Nd, both for In and Sn), which then become amorphous. The magnetic ordering temperatures of all studied RE2Pd2In compounds are dramatically reduced by the hydrogenation, typically to the temperature range below 1.8K.