Critical dynamics at the spin-density-wave transition of chromium

Neutron scattering measurements of the critical fluctuations associated with the spin-density-wave transition at the Neel temperature, T-N approximate to 312 K, in a single-Q chromium crystal are reported. Critical fluctuations are observed emanating from allowed magnetic satellite positions and from satellite positions, corresponding to absent magnetic domains, at which no elastic scattering occurs. The inelastic scattering from these ''silent satellites'' grows rapidly with increasing temperature, becoming equal to the allowed single-Q satellite scattering at T-N. The line shapes of the inelastic scattering at both the allowed and silent satellites are found to be intrinsically asymmetric, reflecting the underlying nesting geometry of the Fermi surface. Energy scans at the silent satellite positions reveal a weakly temperature dependent, characteristic energy below which the observed scattering intensity falls rapidly to zero. (C) 1996 American Institute of Physics.