Neutron-diffraction study of quadrupolar and magnetic order in TmTe.

Neutron-diffraction measurements on the quadrupolar and magnetic-ordered ph ases of TmTe are reviewed. By carefully analyzing the magnetic dipole struc ture induced by an external magnetic field applied along the main symmetry directions, it is possible to determine the nature of the quadrupole order parameter. The data agree qualitatively with the results of a recent mean-f ield model. In particular. the prediction of an extra ferromagnetic compone nt appearing below the Nt ei temperature, due to the preexisting quadrupole order, is confirmed experimentally. Form-factor measurements using polariz ed neutrons are also reported, (C) 2000 Elsevier Science B.V. All rights re served.