Magnetic properties and thermal modification of nanostructured films of nickel nitrides

Nanostructured films of nickel nitrides (from Ni to Ni$_2$N) have been synthesized by magnetron sputtering of a nickel target in an argon atmosphere with the addition of 0.2–70 vol% nitrogen. Magnetization saturation 4$\pi$ $M_S$ and Curie temperature $T_C$ of the solid solution of nitrogen in nickel and nitride Ni$_4$N have been determined. With an increase in nitrogen concentration, 4$\pi$ $M_S$ and $T_C$ decrease, respectively, to 800 G and 490 K. When heated in air, nickel nitride films undergo transformation with nitrogen loss up to phase transitions with structural changes. In particular, heating to 600 K leads to transformation of paramagnetic nitride Ni$_2$N into the ferromagnetic Ni phase in the form of solid solution of nitrogen in nickel.