Small-angle neutron scattering determination of medium and long range order in the amorphous metallic alloy TbCu3.54

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Abstract
Small-angle neutron scattering measurements have been performed on the amorphous metallic alloy TbCu3.54 in its as-prepared state and after annealing for 5 h at 240 degrees C. The sample impurity atoms such as hydrogen, argon and oxygen were identified and their concentrations determined. At very small momentum transfer values a very strong scattering is observed which decreases as q-3 in an oscillatory fashion. A well defined weak ring is observed at about 0.2 AA-1. Annealing doubles the intensity of the whole pattern. In a model description of the observed small-angle scattering, the alloy is composed of domains several thousand of angstroms wide, in which the impurities tend to accumulate near the walls. The impurities might be diluted in the alloy or concentrated such as in small bubbles. In any case, their distribution within the domains is characteristic. The annealing purifies the centres of the domains and repels the impurities to the periphery.