Hydrogen-induced changes in TbNiAl

Neutron diffraction was used to determine the deuterium sites in TbNiAlD1.2 8 and TbNiAlD0.8. Both samples were found to crystallize in the orthorhombi c Amm2 space group. Our analysis reveals that deuterium in TbNiAlD1.28 occu pies positions at x = 0 and x = 1/2. only, while TbNiAlD0.8 shows the forma tion of two different phases. For TbNiAlD1.28, additional magnetic reflecti ons are observed below 16 K indicating antiferromagnetic order. On the othe r hand, at 10 K, only one of the TbNiAlD0.8 phases was found to be magnetic . In addition, our study of the localized vibrations of hydrogen in ToNiAlH (1.39) and in its non-magnetic analog YNiAlH1.35 using inelastic scattering supports the existence of two different hydrogen sites in the saturated hy drides. American Institute of Physics. [S0021-8979(98)33611-7].