Influence of hydrogen absorption on structural and magnetic properties of Ce2Ni2In

Hydrogenation studies were carried out on an intermediate-valence compound Ce2Ni2In. The alloy was found to absorb up to x = 4.98 hydrogen atoms per formula unit at 430 K and at a pressure of 0.3 MPa. The synthesized hydrides were stable in air for a period of few months. The hydrides with x < 2 retain the tetragonal Mo2FeB2-type structure (space group P4/mbm) of the parent compound. For larger hydrogen content a new hydride phase appears with an orthorhombic structure (space group Pbam). Along with the hydrogen uptake in Ce2Ni2InHx there occurs a change in the character of the electronic ground state related to the 4f electrons, from valence fluctuations in the parent compound to rather stable 4f1 configuration in the hydride with x = 4.98. Furthermore, for x = 2.02 and x = 4.98 long-range antiferromagnetic ordering is observed at low temperatures.

Research highlights▶ Determination of stability range of the tetragonal structure of Ce2Ni2In upon hydrogen uptake. ▶ Determination of the upper limit of the hydrogen uptake in Ce2Ni2In. ▶ Description of the evolution of the magnetic behavior in the hydrides Ce2Ni2InHx from valence fluctuations to long-range antiferromagnetic order due to relatively stable 4f1 state.