A small-angle neutron scattering model for polydisperse spherical particles with diffusion zones and application to soft magnetic metallic glass

An analytical expression for the small-angle neutron scattering intensity of diluted systems of polydisperse spherical particles, with diffusion zones, embedded in a matrix is presented. It is used within a nonlinear regression procedure to analyse small-angle neutron scattering experiments with polarized neutrons on an Fe_73.5Si_15.5B₇CuNb₃ alloy. The results for the nuclear and magnetic scattering length densities allow verification of the inhibitor concept introduced for the explanation of the limited sizes of precipitates developing during nanocrystallization. In the case of amorphous Fe_73.5Si_15.5B₇CuNb₃ alloy, the observed nanocrystals of the Fe₃Si type are surrounded by an Nb-enriched shell, which stops the growth of the precipitates. With the results of polarized neutron scattering experiments, it is shown that magnetic and nuclear small-angle neutron scattering signals have the same origin. Additionally, the precision of the fits is improved by complementary use of polarized neutrons.