Synergistic effect of lattice strain and Co doping on enhancing thermal stability in Fe16N2 thin film with high magnetization

Abstract

Single phase Fe16N2 is a potential material in building high-performance magnetic writing heads and permanent magnets due to its ultra-high saturation magnetization (MS) and magnetic anisotropy (Keff). However, the poor controllability of phase constituent and low thermostability (decomposed at 200 °C) are big obstacles to its practical applications. In this work, we have devised a novel Fe/Cr/FeN:Co heterostructure to introduce both lattice strain and Co doping for tuning the FeN constituent and enhancing the phase stability synergistically. With effective regulation, the FeN layer can possesse both superior MS (2.4–2.8 T) and high thermostability with standing 450 °C annealing. Furthermore, by first-principles calculations, we reveal that the synergistic regulation on the thermostability is closely related to the solution heat tunability of Fe-N phases. The Fe/Cr/FeN:Co heterostructure may serve as a promising material for constructing high-efficient writing heads, permanent magnets, and other magnetic devices.