Effect of double nuclear scattering on nuclear-magnetic interference in experiment with small-angle diffraction of polarized neutrons

An experiment on small-angle polarized-neutron diffraction by a two-dimensional spatially ordered array of nickel nanowires embedded in a porous anodic alumina matrix is discussed. The contributions of nonmagnetic (nuclear) structures and nuclear magnetic interference indicating the correlation between magnetic and nuclear structures are discussed. Magnetic scattering is two orders of magnitude smaller than nuclear scattering and, hence, turns out to be weakly distinguishable. The ordered magnetic composite nanostructure of a sample leads to strong interaction between the neutron wave and the structure itself, which, in turn, implies a twofold (miltiple scattering) nuclear scattering process. Nuclear magnetic interference scattering must be analyzed allowing for twofold scattering conditions, which substantially distorts the intensity distribution of the interference contribution of first-order diffraction peaks.