Specific Fe site moment enhancement in Y2Fe17 upon N insertion

Abstract

In order to gain information concerning the separate effects of lattice expansion and Fe–N chemical bonding on the Fe moment for each individual Fe site in R2Fe17Nx systems (R=rare earth), x-ray diffraction, magnetization, and 57Fe nuclear magnetic resonance experiments were carried out on rhombohedral Y2Fe17Nx with N content 0⩽x⩽2.8. The increase of the average 57Fe hyperfine field (HF) from the unnitrided to the nitrided phase follows the increase in the saturation magnetization, providing evidence that the 57Fe HF does scale with the Fe moment in this system. The changes of the 57Fe 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 nearest neighbor. More significantly, for the Fe 6c site, the HF does not 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 picture.