Ferromagnetic thin films of single domain core-shell alpha ''-Fe16N2/Al2O3 nanoparticles (NPs) with average size of 47 nm were prepared by spin coating of the NPs which were well-dispersed to the primary NPs size in toluene by low energy bead-mill dispersion. The magnetic orientation (perpendicular to the Si substrate) was set by applying a magnetic field of 1.2 T during the film formation with a thickness of similar to 1 mu m followed by fixation of the NPs with resin. The SEM and XRD results showed that densely packed assemblies of the NPs were formed and aligned perpendicularly in the film. Based on the magnetic hysteresis curves of the NPs film, the application of the magnetic field during film formation increase the magnetic coercivity (H-c) and remanence (M-r) values of the resulted films by 22.7% and 55.2%. These results demonstrate the potential for nanostructuring bulk magnetic materials comprised of single domain core-shell alpha ''-Fe16N2/Al2O3 NPs. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.