Neutron diffraction studies of the binary uranium stannides USn2 and U3Sn7

Neutron powder diffraction experiments have been performed on the two struc turally related compounds U3Sn7 and USn2. The crystal structures of these t wo compounds were refined for the first time, confirming isotypism with Ce3 Sn7 and ZrGa2 structure types, respectively. The antiferromagnetic ordering suggested by susceptibility measurement on USn2 was confirmed and the magn etic structure was solved. It corresponds to a collinear antiferromagnetic structure with a propagation vector k=(0, 0, 1/2). The magnetic moment deri ved from Rietveld refinement of the neutron powder diffraction pattern at 1 .5 K is 1.56 mu (B)/U. The presence of antiferromagnetic ordering in the U, Sn, compound was confirmed, but the magnetic structure model could not be d etermined due to the very low intensity of the magnetic Bragg peaks, (C) 20 01 Elsevier Science B.V. All rights reserved.