The formation of Fe-N thin films by exposure to an atomic (free radical) nitrogen beam is reported. This new method of preparing Fe-N films uses fluxes of highly reactive, thermal energy N atoms that do not disturb the film microstructure. It is shown that by careful control of the exposure conditions, a range of predominantly single phase films can be obtained. At low nitrogen concentrations an amorphous-like phase is observed, whereas crystalline phases of epsilon -Fe2-3N and zeta -Fe2N are formed at higher concentrations. Dramatic differences in the microstructure and crystallographic texture of these films reveal the inherent microstructure of the different phases rather than the influence of the growth technique.