Variation of magnetic ordering in ε-Fe3N nanoparticles

The magnetic ordering in ε-Fe3N nanoparticles can be controlled by simultaneous variation of the particle size and nitrogen stoichiometry, which can lead to the ferromagnetism at room temperature. In this study, ∼73 nm ε-Fe3−yN1+y (0.1 ≤ y ≤ 0.2) particles with saturation magnetization of 129.0 emu/g at 5 K (close to bulk 133.0 emu/g) are compared to ∼20 nm ε-Fe2.999N1.001 particles. X-ray photoelectron spectroscopy (XPS) studies indicate the formation of nanometric surface oxide/oxynitride layer on the ferromagnetic/superparamagnetic nitride core. The nanoparticles are highly interacting with strong dipolar and exchange interactions. AC-susceptibility measurements confirm the spin-glass-like ordering at lower temperatures.