Nanostructure and magnetic properties of BN-encapsulated Fe(B) and Fe2N nanoparticles prepared by dual ion-beam sputtering

BN-Fe nanocomposite films have been produced by dual ion-beam sputtering codeposition. The effect of using a reactive nitrogen assistance beam during the elaboration process has been studied by transmission electron microscopy, selected area electron diffraction, grazing incidence small-angle x-ray scattering, and magnetic measurements. Experimental results show that without assistance, we produce nearly spherical Fe(B) nanoparticles (2-3 nm in diameter) exhibiting a superparamagnetic behavior. When growing under assistance, we obtain vertically elongated nanoparticles of paramagnetic zeta-Fe2N encapsulated in disordered hexagonal BN. This study demonstrates the possibility of producing encapsulated nanoparticles with high shape anisotropy by activating the surface diffusion of the incoming deposited species. (C) 2003 American Institute of Physics.