Light Scattering by Itinerant Spin-Density Excitation in Metals

Light scattering in metals in the presence of a static spin-density wave is considered. The cross section corresponding to excitation of a electron-hole pair with opposite spin is calculated. It has a threshold of $2g$, where $2g$ is the spin-flip excitation gap. For Cr, the cross section is estimated to be comparable with the cross section for Raman scattering by optical phonons in metals and could be observable.