Neutron diffraction study of YMn2Dx deuterides (1<=x<=3.4)

The YMn2Dx system was studied by means of neutron powder diffraction at temperatures above the magnetic transition in the range 1 less than or equal to x less than or equal to 3.4 D per formula unit. The C15 structure of the YMn2 intermetallic compound is conserved on deuteration. A linear dependence of the cell parameter on deuterium content x was observed. The position and site occupation of deuterium were determined; only the A(2)B(2)-type sites are occupied in this range of concentration. Analysis of the background shows a diffuse contribution attributed to deuterium atom correlations. The site filling and the short-range ordering effect can be explained on the basis of geometrical considerations.