Neutron diffraction and the structure of amorphousNi0.95Tb0.05

Neutron diffraction measurements have been performed on amorphous ${\mathrm{Ni}}_{0.95}$ ${\mathrm{Tb}}_{0.05}$ and crystalline Ni. Thick dc-sputtered films of the amorphous alloy were prepared by high-rate triode magnetron sputtering into liquid-nitrogen-cooled substrates. The contributions of structural and thermal disorder to the first-neighbor radial distribution function were obtained using the crystalline Ni results along with corrections for finite $Q_{\max }$. The results indicate a Ni-Ni first-neighbor structural disorder whose width, ${\sigma }_1$/r${¯}_1$≊3%, is substantially lower than values suggested for amorphous metals. Comparisons with theoretical models of the pair distribution function of a-Ni and a-Fe based on relaxed dense random-packed structures indicate good agreement with the results of Heimendahl. Density measurements have yielded the packing fraction for a-${\mathrm{Ni}}_{0.95}$ ${\mathrm{Tb}}_{0.05}$. Extrapolation of this value has allowed an estimate of the packing fraction of pure a-Ni to be obtained. The results indicate a density greater than the maximum for a hard-sphere, dense random-packing model, but significantly below that of crystalline values found in some relaxed models.