2-MAGNON SCATTERING AND THE SPIN-PHONON INTERACTION BEYOND THE ADIABATIC APPROXIMATION

We consider a model of Raman scattering for a two-dimensional S=1/2 He isenberg antiferromagnet which includes a dynamical spin-phonon intera ction. We observe a broadening of the line shape due to increased coup ling with excited high-energy spin states. Our results are close to a model of random, static exchange interactions, introduced in this cont ext by Haas et al. [J. Appl. Phys. 75, 6340 (1994)], which, when exten ded to large numbers of spins, explains experiments in the parent insu lating compounds of high-T-c superconductors.