APPLICATION OF MODIFIED SPIN-WAVE TO MAGNON-RAMAN SCATTERING PROCESS IN QUANTUM HEISENBERG ANTIFERROMAGNETIC SYSTEM ON A SQUARE LATTICE

The expression of magnon Raman scattering for the case where the sublattice magnetization vanishes by the quantum effect is made for the Heisenberg antiferromagnetic system on a square lattice by the method of modified spin wave, on the basis of the exchange scattering mechanism. We discuss both cases with and without the frustration induced by the exchange interaction for the second nearest neighbor. The numerical calculation for Raman spectra succeeds the theoretical development. Though the quantum fluctuation is expected to be quite strong, it should be stressed that Raman spectra can be expressed as magnon scattering by the exchange scattering mechanism. However, the main peak for two magnon process in those spectra is essentially accompanied by the side peak reflecting four magnon process of the modified spin wave.