Mapping of magnetic excitations in single-Q chromium

The low-energy excitations of antiferromagnetic Cr have been measured by means of inelastic neutron scattering using a novel multi-detector setup on the triple-axis spectrometer IN3 (ILL). A large area in the [010]/[001] scattering plane was investigated around several reciprocal lattice positions in the transverse spin-density-wave phase. The observed intensity map at constant energy transfer E = 6 meV in the Q(k)-Q(l) scattering plane shows rings around (001). The result confirms the recent observation of a dispersive mode perpendicular to the ordering wave vector of the incommensurate structure. In addition, contour maps as measured for various E-transfers indicate the appearance of magnetic intensity at the silent positions (0, +/-delta, 1). (C) 2004 Elsevier B.V. All rights reserved.