Hydrogen induced structural and magnetic transformations in magnetic regenerator materials ErNin (n=1, 2) and HoCu2

The effect of hydrogenation on the structures and magnetic properties of magnetic regenerators HoCu2 (CeCu2-type), ErNi2 (MgCu2-type) and ErNi (FeB-type) has been investigated. All these compounds can form crystalline hydrides which remain in the structure of the original compound. In the case of ErNi2, hydrogenation induces volume expansion up to 13% compared with the parent compound. The magnetic moment and the Curie temperature of the crystalline hydrides decreases as the hydrogen content increases. In the case of ErNi and HoCu2, there is a little change in the lattice parameters and magnetic properties of the crystalline hydrides compared with original compounds. Amorphous hydrides are also observed after the hydrogenation of ErNi2 and HoCu2 compounds.