Neutron diffraction study of ScFe2D compounds

The crystal and magnetic structures of ScFe 2 and its deuteride ScFe 2 D 3.2 have been investigated by neutron powder diffraction. The C14 hexagonal MgZn 2 -type crystal structure of the initial alloy ScFe 2 is maintained upon the insertion of 3.2 D/f.u.. Deuterium localization within the crystal lattice reveals occupancy of four tetrahedral interstitial sites, each coordinated by two Sc and two Fe atoms. Among these, the 6 h 2 and 12 k 1 sites are filled at 77 % and 27 % respectively, while the 24 l and 6 h 1 are less than 20 % occupy. The magnetic moment magnitudes have been determined for the two inequivalent Fe sites (2 a and 6 h ) using Rietveld analysis of the magnetic structure; both increase with deuterium insertion. It is found that the magnetic moment orientation at low temperature changes upon deuterium absorption. For ScFe 2 , the Fe magnetic moments are aligned at an angle of 30° with respect of the c -axis, whereas for ScFe 2 D 3.2 they lie within the basal plane of the hexagonal structure. We also report the thermal evolution of the lattice parameters for both compounds over the temperature range of 2 K to 300 K. ScFe 2 exhibits typical thermal expansion behavior bellow 300 K, while ScFe 2 D 3.2 displays unusual lattice parameters variations with temperature. • C14 hexagonal MgZn 2 -type structure of ScFe 2 is preserved upon deuterium insertion. • D interstitial sites in ScFe 2 D 3.2 structure determined using neutron diffraction. • Magnetic structure of ScFe 2 changes upon deuterium insertion. • Unusual thermal variation of the lattice parameters is observed for ScFe 2 D 3.2 .