Neutron diffraction study of Ho5YFe23 and Ho5YFe23D16 deuteride

Neutron diffraction experiments (LLB) were performed on Ho5YFe23Dz and its parent alloy Ho5YFe23 to determine the localization of deuterium atoms, precise their magnetic structures and compare to previously determined low magnetic field magnetization properties of Ho6−xYxFe23Hz (0≤x≤6; z=16). In both alloy and deuteride, the Fe moments are coupled ferromagnetically to each other and antiferromagnetically to the rare-earth. At low temperature, the magnetic moment of Ho is slightly less than its free ion value (9.2 μB  at.−1 versus 10 μB  at.−1). A decrease of the magnetic Ho-Fe exchange interaction is observed in relation to the increase of atomic distances upon hydrogenation. In comparison to parent alloy, absorption of hydrogen leads to a decreasing Tcomp, a strong increase of the Fe magnetic moment. A canting model gives a slightly better fit of the neutron data as compared to a pure ferrimagnetic model. The mean canting angle is small (θ<10°) in agreement with Herbst and Croat refined-Néel molecular field model used in the discussion of the magnetization experiments.