Effect of Nitrogen Uptake on the Curie Temperature of Intermetallic Compounds R2Fe17 and R2Fe17C0.5

Abstract
We studied the effect of nitrogen uptake on the Curie temperature T c and the lattice constants a and c in the R 2Fe17 and R2Fe17C0.5 systems. Both the lattice constants increase by about 1.3 to 3% without changing crystal structures after full uptake of nitrogen, indicating that the nitrogen atoms occupy interstitial sites. The T c increases by 230 K to 480 K upon nitriding, and the R dependence becomes markedly weak compared to that of the host R2Fe17 compound series. The results obtained suggest that the rise of T c strongly correlates with the rate of increase of lattice constant a due to nitrogen introduction.