Observation of cross-shaped anisotropy in spin-resolved small-angle neutron scattering

Abstract

We report the results of spin-resolved small-angle neutron scattering (SANS) experiments on the two-phase nanocrystalline alloy NANOPERM. At a saturating applied magnetic field of $1.27\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ we observe a cross-shaped angular anisotropy in the non-spin-flip SANS cross section ${\ensuremath{\Sigma}}^{++}$. This feature---for this class of materials only visible at saturation in ${\ensuremath{\Sigma}}^{++}$---is attributed to the specific ratio of nuclear to magnetic scattering being smaller than unity. Analysis of the non-spin-flip and spin-flip cross sections provides the nuclear and magnetic SANS and allows us to estimate the magnitude of the respective scattering-length density contrast at the interphase between the nanoparticles and the amorphous magnetic matrix.