Films with nanocomposite structure αFe(N) +ZrN for soft magnetic applications

•Films Fe(79-78)Zr(10)N(11-12) produced by RF magnetron sputtering were studied.•Metastable nanocomposite structure forms in the as-sputtered films.•The annealing of the films leads to a shift of the metastable state to equilibrium.•αFe+ZrN nanocomposites exhibit the properties required for soft magnetic applications. Film nanocomposite structure αFe(N) + ZrN is able to ensure properties required for application of the films in modern magnetic microelectronics. To form the nanocomposite structure, the Fe79-78Zr10N11-12 films, which were prepared by long-duration (100 and 250 min) reactive magnetron sputtering characterized by the extremely low film deposition rate (7 nm/min), were subjected to annealing (at 300-600°C for 1 h.). In the case of sputtered films, the formation of the mixed structure consisting of two nanocrystalline (the supersaturated nitrogen solid solution in αFe and nonstoichiometric Zr1N1-X nitride) and amorphous phases was shown by x-ray diffraction analysis and conversion Mössbauer spectroscopy. To be the prerequisite for the nanocomposite structure, the phase composition of sputtered films should be metastable and slightly shifted towards the equilibrium. The latter is realized when a proper relationship of thermodynamic and kinetic features of the system is established in the course of deposition of the films. The evolution of the prerequisite state during annealing leads to the equilibrium state characterized by the nanocomposite structure (αFe(N) + Zr1N1-X). Static magnetic properties of the as-sputtered films and the films subsequently annealed at 500°C were measured, and the structural justification of the reached properties was presented. The analysis of the quantitatively estimated structural parameters of the annealed films, taking into account the fundamental concepts of the soft magnetic properties (saturation magnetization and coercive field), provides an opportunity to choose purposefully the conditions of the prerequisite phase state and desirable composite structure. The metastable state formed in the as-sputtered films is substantiated based on fundamentals of the materials science and metal physics. The films after annealing at 500°C show a coercive field of less than 159 A/m and a saturation induction of at least 1.4 T.