Thermal stability of partially ordered Fe₁₆N₂ film on non-magnetic Ag under layer

Partially ordered Fe₁₆N₂ thin film with (001) texture is successfully grown on a Ag under layer using a facing target sputtering system. Fe₁₆N₂ phase is formed after post-annealing, which is detected by X-ray diffraction (XRD). High saturation magnetization (M _s) of Fe₁₆N₂ thin films is observed by vibrating sample magnetometry. It is found that Fe₁₆N₂ phase can be stable up to 225°C, which is demonstrated by the Fe ₁₆N₂ finger print peak (002) in XRD. After heating to 250°C, the Fe₁₆N₂ phase decomposes, which leads to low M_s and soft magnetic behavior. To further study Fe ₁₆N₂ decomposition, X-ray photoelectron spectroscopy is performed to detect the binding energy of nitrogen atoms. Differences of binding energy corresponding to before and after heat treatment show the variation of nitrogen atom in electronic state with surrounding Fe atoms, indicating nitrogen atomic migration during heat treatment.