Neutron diffraction studies of the binary uranium stannides USn 2 and U 3Sn 7

Abstract

Neutron powder diffraction experiments have been performed on the two structurally related compounds U 3Sn 7 and USn 2. The crystal structures of these two compounds were refined for the first time, confirming isotypism with Ce 3Sn 7 and ZrGa 2 structure types, respectively. The antiferromagnetic ordering suggested by susceptibility measurement on USn 2 was confirmed and the magnetic structure was solved. It corresponds to a collinear antiferromagnetic structure with a propagation vector k=(0, 0, 1/2). The magnetic moment derived from Rietveld refinement of the neutron powder diffraction pattern at 1.5 K is 1.56 μ B/U. The presence of antiferromagnetic ordering in the U 3Sn 7 compound was confirmed, but the magnetic structure model could not be determined due to the very low intensity of the magnetic Bragg peaks.