We have performed small-angle polarized neutron scattering experiments of spherical Fe16N2 nanoparticles, which are potential candidate materials for high density magnetic recording tape. The results were analyzed based on a core-shell model, and we evaluated the magnetic structure of the particles. The correlation between the magnetic structure and magnetic stability of the particles were discussed in terms of high density recordings. (C) 2009 Elsevier B.V. All rights reserved.