THEORY OF RAMAN-SCATTERING ON SPIN FLUCTUATIONS IN NEARLY ANTIFERROMAGNETIC SYSTEMS

The role of the spin degrees of freedom in Raman scattering from the antiferromagnetic, undoped high temperature superconductors is well understood. In the doped materials, however, where the magnetic correlation length is finite, the situation is less clear. In this paper we consider the scattering of light from low energy collective spin excitations in almost antiferromagnetic systems which we propose as a new mechanism for Raman scattering in these materials. We present results for the temperature and the frequency dependence of the Raman scattering intensities from hydrodynamic long wavelength spin modes as well as from slow fluctuations of the staggered spin density.