RNiAl hydrides and their magnetic properties

RNiAl compounds absorb hydrogen at normal pressure typical to a stoichiometry of RNiAlH∼1.4. Thermal desorption studies showed that, besides such hydrides, several partly decomposed hydrides with lower H concentrations are also stable. The X-ray analysis shows that, in most cases, hydrogenation leads to an orthorhombic distortion of the original hexagonal structure of the ZrNiAl type. The hydrogenation severely affects magnetic properties depressing ordering temperatures and changing all the magnetic phase diagrams. (orig.)