A MOSSBAUER-EFFECT STUDY OF THE INTERSTITIAL HYDRIDES AND NITRIDE OF ND2FE17

The Mossbauer effect spectra of Nd2Fe17H3, Nd2Fe17H5, and Nd2Fe17N3 ha ve been measured at several temperatures between 85 and 295 K and fitt ed with a model which is similar to that used for the analysis of the Mossbauer effect spectra of Nd2Fe17 and Nd2Fe17N2.6. The weighted aver age isomer shift increases in going from Nd2Fe17 to its hydrides and n itride, an increase which results mainly from the lattice expansion. T he changes in the individual isomer shifts upon hydrogenation may be u nderstood in terms of the expansion of the Wigner-Seitz cell volume an d the presence of hydrogen or nitrogen near neighbors at a specific si te. The 295 K weighted average hyperfine field increases from 157 kOe in Nd2Fe17 to 243 kOe in Nd2Fe17H3, 280 kOe in Nd2Fe17H5, and 318 kOe in Nd2Fe17N3, a sequence determined by the Curie temperatures. In cont rast, the weighted average hyperfine field at 85 K and the saturation magnetization at 5 K for Nd2Fe17H3 are lower than those of Nd2Fe17, pr esumably because of the c-axis lattice contraction which occurs upon h ydrogenation of this compound. The main difference between the effect of hydrogenation and nitrogenation resides in the substantial increase observed for the 9d and 18h hyperfine fields upon nitrogenation.