MAGNETIC RAMAN-SCATTERING IN 2-DIMENSIONAL SPIN-1/2 HEISENBERG ANTIFERROMAGNETS - SPECTRAL SHAPE ANOMALY AND MAGNETOSTRICTIVE EFFECTS

We calculate the Raman spectrum of the two-dimensional spin-1/2 Heisenberg antiferromagnet by exact diagonalization and quantum Monte Carlo techniques on clusters of up to 144 sites. On a 16-site cluster, we consider the phonon-magnon interaction which leads to random fluctuations of the exchange integral. Results are in good agreement with Raman scattering experiments on various high-T-c precursors, such as La2CuO4 and YBa2Cu3O6.2. In particular, our calculations reproduce the broad line shape of the two-magnon peak, the asymmetry about its maximum, the existence of spectral weight at high energies, and the observation of nominally forbidden A(1g) scattering.