SPECIFIC FE SITE MOMENT ENHANCEMENT IN Y2FE17 UPON N INSERTION

In order to gain information concerning the separate effects of lattic e expansion and Fe-N chemical bonding on the Fe moment for each indivi dual Fe site in R2Fe17Nx systems (R=rare earth), x-ray diffraction, ma gnetization, and Fe-57 nuclear magnetic resonance experiments were car ried out on rhombohedral Y2Fe17Nx with N content 0 less than or equal to x less than or equal to 2.8. The increase of the average Fe-57 hype rfine field (HF) from the unnitrided to the nitrided phase follows the increase in the saturation magnetization, providing evidence that the Fe-57 HF does scale with the Fe moment in this system. The changes of the Fe-57 HF are not the same for the various Fe sites; e.g., the HF at the 18f site, which has one N atom as a nearest neighbor, has much less enhancement than that at the 9d site, which has no N atoms as a n earest neighbor. More significantly, for the Fe 6c site, the HF does n ot change at all with nitrogen content. These results are analyzed in conjunction with existing neutron diffraction data regarding the Fe-Fe distance variations upon nitrogenation and yield a very consistent pi cture. (C) 1997 American Institute of Physics.