Polarised neutrons and axial-vector interactions in magnetic materials

Inelastic polarised neutron scattering is analysed when the magnetic intera ction includes a part characterised by an axial vector. In this case the dy namical chiral (DC) scattering and inelastic nuclear-magnetic interference (INMI) may appear. As examples we consider magnetic field and antiferromagn ets with k(AF) = 0. Possibilities of other axial-vector interactions such a s the Dzialoshinskii-Moriya interaction and elastic torsion are mentioned t oo. The DC scattering in magnetic field is determined by the three-spin cor relations. Their experimental investigation in iron above T, allows to conf irm predictions of the Polyakov-Kadanoff-Wilson operator algebra and demons trate crossover to the dipolar critical dynamics. The INMI in the antiferro magnets with k(AF) = 0 is considered theoretically and appearance of the in fra-red divergence in the case of quasi-2D compound BaNi2(PO4)(2) was demon strated. (C) 2001 Elsevier Science B.V. All rights reserved.