Microstructure and magnetic properties of iron nitride thin films

A series of iron nitride thin films with thickness d ranging from 38 to 182 nm were fabricated on silicon (1 0 0) substrates by reactive rf magnetron sputtering in a N2–Ar atmosphere. The microstructure and magnetic properties have been investigated systematically. It was found that the resistivity of iron nitride films is up to 190 μΩ cm. Due to the in-plane applied magnetic field (50 Oe), iron nitride films with d ⩽ 119 nm are amorphous or nano-crystalline structure, while the polycrystalline γ′-Fe4N samples are obtained as d ⩽ 182 nm. Iron nitride films with d ⩽ 119 nm exhibit in-plane uniaxial magnetic anisotropy and excellent soft magnetic properties. However, Iron nitride films with d = 182 nm show isotropy property with coercivity of 72 Oe. Furthermore, the investigation of dynamic magnetic properties shows that the resonance frequency of the iron nitride films with d ⩽ 119 nm are in the range 1.1–2.2 GHz. As a consequence, the applied magnetic field (50 Oe) has a significant influence on the magnetic properties and microstructure of iron nitride thin films.

•Iron nitride films with d ⩽ 119 nm exhibit in-plane uniaxial magnetic anisotropy.•Iron nitride films with d = 182 nm show isotropy property with coercivity of 72 Oe.•An applied magnetic field (AMF) can prevent the crystallization of the sample.•The resonance around gigahertz were observed for iron nitride films d ⩽ 119 nm.•As deposited iron nitride films have much potential for high-frequency application.