Polarization dependence of the magnetic fluctuations in Cr below

We have investigated the magnetic excitations in single-Q, single-domain Cr below (Formula presented) using polarization analysis of inelastically scattered neutrons for energy transfers up to 18 meV. The results show that the longitudinal (Formula presented) magnetic modes are enhanced below (Formula presented) with respect to the transverse (Formula presented) modes at low temperature. The latter are independent of the polarization with respect to the ordering vector (Formula presented) in the transverse spin-density-wave phase, i.e., they are isotropic. The (Formula presented) and (Formula presented) modes are not affected by the spin-flop transition to the longitudinal spin-density-wave phase at (Formula presented) indicating that the transition is due to anisotropies and that it is not an intrinsic feature of the spin-density wave. There are indications that the (Formula presented) modes have a less steep dispersion curve and are more damped than the (Formula presented) modes in accordance with the three-band model by Fishman and Liu. With increasing temperature the intensity from the (Formula presented) and (Formula presented) modes increases strongly at small (Formula presented) transfer and their (Formula presented) dependence becomes similar. In particular, the enhancement of the (Formula presented) modes with respect to the (Formula presented) modes vanishes. Significant inelastic scattering is present at the silent peak positions. It surpasses even the scattering at the allowed peak positions at large (Formula presented) transfers. We argue that the silent inelastic scattering is partly responsible for the “commensurate” scattering at the (100) position due to resolution effects and that the major cross section at (100) is due to the longitudinally polarized Fincher-Burke mode at 4.2 meV.