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Neutron diffraction experiments were performed on a single crystal of alpha-uranium in the phase below 43 K, in which a charge-density wave (CDW) exists. The superspace group in the CDW state is identified as primitive monoclinic, in agreement with recent theoretical predictions. The CDW state below 37 K consists of two coherent q vectors existing within the same crystal volume, and this coexistence gives rise to additional interference effects. At 22 K, the component of the CDW in the [010] direction locks into a commensurate value of 1/6. Associated with this lock-in, higher-order satellites of third, fifth, seventh, and ninth harmonics of the total CDW distortion appear below 30 K. Elastic diffraction effects extend over six decades of intensity. The presence of higher odd-order harmonics indicates a squaring of the CDW displacement, but this is incomplete even at the lowest temperatures. Unusual domain effects are found near the 22 K lock-in phase transition.

Additional information

Authors: MARMEGGI J C, Centre National de la Recherche Scientifique, Laboratoire de Cristallographie, Grenoble (FR);LANDER G H, JRC Karlsruhe (DE);VAN SMAALEN S, University of Groningen, Materials Science Center, Groningen (NL);BRÜCKEL T, Institut Laue Langevin, Grenoble (FR);ZEYEN C M E, Institut Laue Langevin, Grenoble (FR)
Bibliographic Reference: Article: Physical Review B, Vol. 42 (1990) No. 15, pp. 9365-9376
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