Interstitial alloys as hard magnetic materials

Abstract For clarifying the role that the interstitial N atoms played on the microscopic scale for basic magnetism in R2Fe17N3, we determined the enhancements of Fe magnetic moments on the crystallographically different atomic sites and crystalline electric field parameter A20 upon nitrogenation by neutron diffraction studies of the rhombohedral Y2Fe17 and Y2Fe17N3.1 and high-field magnetization measurements of single crystalline Nd2Fe17 and Nd2Fe17N3, respectively. The results obtained are compared with those estimated by the band structure calculation. For clarifying the coercivity mechanism in Sm2Fe17N3, we also examined the particle (powder) size and surface cleaning effects on the coercive field μ0Hc for the Sm2Fe17N3 single crystal powder. The results indicate that μ0Hc monotonically decreases with increasing the particle size, suggesting that the coercivity mechanism is of a nucleation type. When there are many nucleation sites on the surface of Sm2Fe17N3 powder before surface cleaning, the value of μ0Hc is relatively small and reveals strong temperature dependence, while μ0Hc is strongly enhanced by surface cleaning, leading to relatively weak temperature dependence.