Magnetic properties and155Gd Mossbauer effect in GdCu2and its ternary hydride

Abstract

The magnetic and crystallographic properties of GdCu2 and its ternary hydride GdCu2Hx have been investigated. Upon hydrogen absorption the crystal structure of GdCu2 changes from orthorhombic (CeCu2-type) to tetragonal (MoSi2-type), accompanied by a lattice expansion of 29%. The uncharged intermetallic compound GdCu2 orders antiferromagnetically (TN=37K). After H2 absorption it becomes ferromagnetic (TC=45K). There is a strong increase in the asymptotic Curie temperature (from theta p=7K to theta p=57K). Studies of the 155Gd Mossbauer effect in the uncharged and charged compounds show that the H2 absorption leads to an increase in isomer shift and in the absolute value of the hyperfine field at 4.2K. Both changes have been discussed in terms of a changing conduction electron concentration.