Variation of magnetic ordering in ε-Fe3N nanoparticles

► ∼70 nm ε-Fe3N nanoparticles are ferromagnetic at room temperature and the saturation magnetization at 5 K reaches close to the bulk value (133 emu/g) ► ∼20 nm ε-Fe3N are superparamagnetic at room temperature and the magnetization is significantly lower ► Magnetization depends on nitrogen stoichiometry in the nitrides as well as particle size ► The ε-Fe3N nanoparticle surface consists of nm-thick oxide/oxynitride layers ► Spin-glass-like ordering exists at low temperatures ► The nanoparticles are highly interacting with strong dipolar interactions and exchange-like interactions