EFFECT OF INTERSTITIAL HYDROGEN AND NITROGEN ON MAGNETIC AND STRUCTURAL-PROPERTIES OF R(2)T(17) (R-Y, CE AND SM T-FE, CO AND NI)

In order to clarify the influence of interstitial H and N on the basic magnetism, we carried out X-ray diffraction and magnetic studies of R(2)T(17) hydrides and nitrides with R=Y, Ce or Sm and T=Fe, Co or Ni. The saturation magnetic moment M(s) of Y2Fe17 increases from 34.0 to 39.7 mu(B) for an N uptake of 3.0 atoms per formula unit, whereas M(s) in Y2Fe17Hx decreases from 34.0 to 32.4 mu(B) for x=3.0 and then recovers to 34.4 mu(B), for x=4.6. The Curie temperature T-c of Y2Fe17 increases from 300 to 701 K upon nitrogenation and to 481 K for an H uptake of x=3.0. On the other hand, both M(s) and T-c of Y2Co17 decrease markedly upon hydrogen and nitrogen absorptions. Furthermore, upon introduction of H atoms into Y2Ni17 it loses its ferromagnetism and becomes paramagnetic even at 4.2 K. For Ce2Fe17, nitrogenation brings about a dramatic change in the 4f electron character from itinerant to localized states. The results obtained are discussed on the basis of the calculated electronic band structures.