Small-angle neutron scattering of the system Fe80−xNixB12Si8 in the amorphous state with 0 ⩽ x ⩽ 80: comparison with the evolution of crystallization studied by the controlled Joule effect analysis

The evolution of crystallization of amorphous ribbons has previously been studied by the controlled Joule effect analysis (CJEA) in the system Fe80−xNixB12Si8. The sign and magnitude of resistivity changes due to the relaxation depend strongly on the Ni/Fe ratio. The anomalous behavior observed during crystallization was explained by large fluctuations of local environments of Ni and Fe atoms which have a high mobility in these glasses. Depending on x, small amorphous local units with different atomic compositions would be present in the glassy matrix. To confirm these results, the small-angle neutron scattering (SANS) of: these amorphous alloys has been measured at room temperature. A significant contribution to the SANS intensity is observed for all the alloys. The radii of gyration of the scattering particles depend on x and vary between 230 and 300 Å. Except for 50 < x < 65, an interference peak present in the intensity curves confirms the presence of numerous other aggregates for which the radii of gyration are distributed between 65 and 90 Å and their mean distances between 300 and 400 Å. Sizes and distances have been determined with an accuracy equal to ±10% using more than one approximation method. Their rough volume has been evaluated from the normalized intensities assuming spherical form and particular compositions defined from the X-ray patterns. The presence of aggregates in the glasses partially explains the anomalous behavior of resistivity but it is not possible to confirm the real composition of these aggregates for all x-values.