Thermodynamic and magnetic properties of GdPd hydride

Thermodynamic and magnetic properties of GdPd hydride (deuteride) were studied. Each of the pressure-composition isotherms of GdPd-Q (Q = H or D) systems showed a plateau region in 0.05 < [Q]/[GdPd] < 0.4, though hydrogen induced disproportionation of GdPd was observed above [Q]/[GdPd] > 0.4. The disproportionation products were determined to be GdQ₂ and Gd₃Pd₄. Enthalpy changes for GdPd hydride formation at [Q]/[GdPd] = 0.2 were evaluated from the isotherms to be ΔH_fo = -130kJ/mol_H2 and -122kJ/mol_D2. Magnetization measurements revealed that the effective magnetic moments of GdPd and its hydride were approximately the same as that of Gd³⁺. This indicates that magnetic properties of GdPd and its hydride are governed by gadolinium atoms. In fact, the magnetic ordering temperature and the paramagnetic Curie temperature were also found to be almost invariable with hydrogen content, revealing that electrons from the Is orbital of absorbed hydrogen bring little influence on the nature of 4f-electrons of gadolinium. [doi: 10.2320/matertrans.MRA2007307]