Neutron Diffraction Study of Nd2Fe16TiDy at 300 and 1.5 K

Abstract

The 300 and 1.5 K powder neutron diffraction patterns of Nd 2 Fe 16 TiD y have been measured. A Rietveld refinement of these data yields the Nd 2 Fe 16.3 Ti 0.7 D 4.8 stoichiometries for the compound. It indicates also that titanium occupies only the 6c crystallographic site and hydrogen the 9e and the 18h sites in the rhombohedral structure. The insertion of interstitial hydrogen produces a 4% increase in the unit-cell volume of the titanium compound at room temperature. In the range of 1.5 K, the parameter a decreases, but the parameter c increases. This phenomenon indicates that the thermal expansion along the c-axis exists despite of the occupancy of the 6c site by titanium. By insertion of hydrogen, the Curie temperature and the saturation magnetization increase.