Structural and magnetic properties of ammonia-nitrided

In order to make a comparison with N2-gas nitrogenation, the structural and magnetic properties of ammonia-nitrided Y2Fe17Nx were investigated by a combination of x-ray diffraction, magnetization and nuclear magnetic resonance. It was found that by using NH3, the nitrogenation temperature and/or time are greatly reduced, and nominal N concentrations 0 6 x 6 6:3 are obtainable. For lower N content,x6 3:3, a two-phase (nitrided + unnitrided) configuration exists in the sample particles. The unnitrided phase is completely suppressed for x> 3:8; however, an amorphous-like phase appears for x> 5:6. The average value for the magnetic moment per Fe atom initially increases with the N content, reaching a maximum forx 4 before decreasing. The magnetic anisotropy, which arises solely from the Fe sublattice, is reduced for higher N content, but is still basal planar. These results indicate that the microscopic structure of the nitrided phase in ammonia-nitrided Y2Fe17Nx is different from that in the same material prepared by N2-gas nitrogenation. Evidence is provided for the existence of more than three, most likely four, nitrogen atoms per formula unit in the nitrided phase when x> 3.