Structural and magnetic properties of ammonia-nitrided Y2Fe17

In order to make a comparison with N-2-gas nitrogenation, the structural an d magnetic properties of ammonia-nitrided Y2Fe17Nx were investigated by a c ombination of x-ray diffraction, magnetization and nuclear magnetic resonan ce. It was found that by using NH3, the nitrogenation temperature and/or ti me are greatly reduced, and nominal N concentrations 0 less than or equal t o x less than or equal to 6.3 are obtainable. For lower N content, x less t han or equal to 3.3, a two-phase (nitrided + unnitrided) configuration exis ts in the sample particles. The unnitrided phase is completely suppressed f or x greater than or equal to 3.8; however, an amorphous-like phase appears for x greater than or equal to 5.6. The average value for the magnetic mom ent per Fe atom initially increases with the N content, reaching a maximum for x approximate to 4 before decreasing. The magnetic anisotropy, which ar ises 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 i n the same material prepared by N-2-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.