Hydrogenation-induced changes of the crystal structure and magnetic properties of Er2Ni2Sn

Abstract Hydrogenation of the intermetallic compound Er2Ni2Sn (Mo2FeB2-type structure) was studied. The hydride Er2Ni2SnH3.5 was formed under a hydrogen pressure of 65 kPa, after heating up to 373 K. The structure type of the metal sublattice was preserved, but the hydrogenation resulted in anisotropic lattice expansion prevailing in the crystallographic direction c. A lower hydride, Er2Ni2SnH3.5-х, was obtained by heating Er2Ni2SnH3.5 up to 573 K in dynamic vacuum. For Er2Ni2SnH3.5-х the lattice expansion in the ab plane was accompanied by a reduction of the lattice parameter c. Er2Ni2Sn is an antiferromagnet with TN = 6.1 K, whereas the hydrides Er2Ni2SnH3.5 and Er2Ni2SnH3.5-х remain paramagnetic down to 2 K (limit of the measurements). Hydrogenation results in weakening of the magnetic interactions, in agreement with the decrease of the conduction electron concentration caused by chemical bonding between hydrogen and metal atoms.