Thermal stability of Fe₁₆N₂ thin film on GaAs (0 0 1) substrate

There is a major need for a high performance magnetic system for high temperature applications. One propitious low cost permanent magnet candidate is Fe 16 N 2 , with its giant magnetic moment predicted to be above other materials from conventional first principles calculations. Here we report on a comprehensive study of the thermal stability of Fe 16 N 2 thin films on GaAs (0 0 1) substrate. Using polarized neutron reflectometry (PNR), the saturation magnetization depth profile (Ms) of the films and its modification with temperature is directly measured at various thermal conditions. The structural modifications probed by x-ray diffraction (XRD) unravel that above 250 °C the Fe 16 N 2 thin films decompose into α -Fe and γ ′-Fe 4 N phases. An influence of the strain effect is investigated by grazing incidence x-ray diffraction (GIXRD). We reveal that despite a large Fe 16 N 2 in-plane lattice constant of ~5.88 Å and different strains from substrate or seed layer (up to 2.8% tensile strain), Fe 16 N 2 thin films have the same thermal stability. Our results demonstrate that the high thermal stability of partially order Fe 16 N 2 thin films makes them very promising candidates for spintronics and permanent magnet applications.