Neutron diffraction study of Nd2Fe16TiDy at 300 and 1.5 K

The 300 and 1.5 K powder neutron diffraction patterns of Nd2Fe16TiDy have b een measured. A Rietveld refinement of these data yields the Nd2Fe16.3Ti0.7 D4.8 stoichiometries for the compound. It indicates also that titanium occu pies only the 6c crystallographic site and hydrogen the 9e and the 18h site s in the rhombohedral structure. The insertion of interstitial hydrogen pro duces a 4% increase in the unit-cell volume of the titanium compound at roo m temperature. In the range of 1.5 K, the parameter a decreases, but the pa rameter c increases. This phenomenon indicates that the thermal expansion a long the c-axis exists despite of the occupancy of the 6c site by titanium. By insertion of hydrogen, the Curie temperature and the saturation magneti zation increase.