Nuclear magnetic resonance study of R2Fe17 (R=Y, Sm, and Gd) hydrides

In order to study the location of hydrogen atoms and the effects of their insertion into R2Fe17, spin–echo NMR experiments have been carried out on the hexagonal Y2Fe17H x (x=0, 3.0, 4.7), rhombohedral Sm2Fe17H x (x=0, 1.7, 5.7), and mixed‐phase Gd2Fe17H x (x=0, 2.3, 5.8) compounds. 1H and 89Y spectra obtained from Y2Fe17H x clearly demonstrate that the hydrogenation process is reversible upon vacuum annealing. For both Y2Fe17H x and Sm2Fe17H x , the 1H spectra show two broad peaks; the peaks are tentatively assigned to H atoms in the tetrahedral and octahedral interstitial sites, and a hydrogen filling scheme is proposed. For Gd2Fe17H x , a single broad 1H peak near 70 MHz is observed; application of an external magnetic field indicates that the hyperfine field has the same direction as the net magnetization.