We present a study of polycrystalline thin films of the rock salt rare earth nitride GdN grown on amorphous fused silica at ambient temperature with varying N 2 pressure. X-ray diffraction measurements show a strong (111) preferential orientation for all N 2 pressure and the signature of a secondary phase of GdN that develops as the N 2 pressure decreases. The secondary phase is found to have a smaller lattice parameter than the near-stoichiometric GdN. Raman spectroscopy, electrical and magnetic results support the coexistence of such mixed-phase samples with the lattice distortion originating from nitrogen vacancies. Significantly the magnetic data show an increase of the ferromagnetic onset temperature as the secondary phase develops, without affecting the soft ferromagnetic character of GdN.