Structural, magnetic, and Mossbauer spectral study of Er2Fe17 and its hydrides

The structural and magnetic properties of the Er2Fe17Hx compounds, where x is 0, 1, 2, 3, and 3.8, have been investigated by means of powder x-ray diffraction, thermal and ac magnetic susceptibility measurements, and iron-57 Mossbailer spectroscopy. The Er2Fe17Hx compounds crystallize in the hexagonal P6(3)/mmc space group with the Th2Ni17-like structure, a structure which has both an iron-rich stoichiometry and disorder of the erbium and iron-iron 4f-4f dumbbell sites. The increase in the lattice parameters, the magnetic ordering temperature, the saturation magnetization, and the dependence of the Mossbauer spectral hyperfine parameters upon the hydrogen content reveal a two-step filling of the interstitial sites, with hydrogen first filling the octahedral 6h sites for x<3 and then partially filling the tetrahedral l2i sites for x = 3 and 3.8. Neither the Mossbauer spectra nor the ac magnetic susceptibility measurements reveal any spin reorientation in any of these compounds. In all of the compounds both the excess amount of iron and the expected disorder is confirmed by the Mossbauer spectra and the hyperfine parameters of the iron 4e site are reported herein. Finally, the Mossbauer spectra indicate that the interstitial hydrogen atoms partially occupying the tetrahedral 12i sites are jumping between these sites on the Mossbauer time scale.