Neutron diffraction study of the structural and magnetic properties of ε-Fe<inf>3</inf>N<inf>1.098</inf>and ε-Fe<inf>2.322</inf>Co<inf>0.678</inf>N<inf>0.888</inf>

Abstract

Binary ε-Fe 3 N 1.098 and ternary ε-Fe 2.322 Co 0.678 N 0.888 were synthesized as spherical bulk materials using novel high-pressure solid-state metathesis reactions (HPSSM). The structural and magnetic properties of the two nitrides were investigated using neutron powder diffraction (NPD), a vibrating sample magnetometer (VSM), and first-principle calculations. We found that at high pressure and high temperature (HPHT), nitrogen atoms enter the interstitial 2d sites of the nitrogen-rich ε-Fe 3 N 1.098 structure, space group P6 3 22, which were previously reported to be vacant. The stoichiometry of the nitride (N/Me ratio) and the level of disorder have a significant influence on the site occupancies and local magnetic moments in these iron-based nitrides. The substitution of Fe by Co in ε-Fe 2.322 Co 0.678 N 0.888 did not reduce the mean magnetic moment (μ m ) per metal atom at the Wyckoff 6 g site. NPD refinements showed that the magnetic moment per Fe atom in ε-Fe 3 N 1.098 (at 1.8 (4) μ B ) was slightly higher than that of ε-Fe 2.322 Co 0.678 N 0.888 , where the moment per Fe/Co atom is 1.7(2) μ B .