  We have used numerical micromagnetics for the calculation of the magnetic
(small-angle) neutron scattering cross section of nanocomposites. The novel
aspect of our approach consists in the possibility to study the applied-field
dependence of the individual contributions to the total magnetic scattering.
Such a micromagnetic tool ideally complements neutron experiments in which one
generally measures only a weighted sum of the Fourier components of the
magnetization. The procedure furnishes unique and fundamental information
regarding the magnetic microstructure and corresponding magnetic scattering
from nanomagnets. In particular, our simulation results explain the recent
observation of dipolar correlations in two-phase nanocomposites and provide an
answer to the question of the explicit dependence of the magnetization Fourier
coefficients on the scattering vector.
