MAGNETIC EXCITATIONS IN SPIN-DENSITY-WAVE (SDW) STATE OF CR

Inelastic neutron scattering in the SDW state of Cr at 54 K revealed a complex dynamical structure in Q. Magnetic scattering centered at the commensurate wave vector of (1 0 0) is observed in addition to the scattering centered at the incommensurate wave vector of SDW. Integrated intensities, integral dQchi''(Q, omega), for commensurate scattering increase linearly with the excitation energy, but those of the incommensurate scattering saturate at 15-20 meV. The crossover from the coexisting state of the commensurate and incommensurate spin fluctuations to the state in which the commensurate scattering is dominant, occurs at 30-40 meV. This new result questions the validity of a simple linear spin-wave approximation in the SDW state of Cr.