2-MAGNON RAMAN-SCATTERING IN KNIF3 - A COMPARISON OF EXPERIMENT WITH MONTE-CARLO CALCULATIONS IN THE ORDERED AND DISORDERED REGIONS

Using Raman scattering we have investigated the behaviour of two-magno n excitations in KNiF3 in dependence on the temperature especially at and above the Neel temperature (T-N). The shift of the two-magnon peak position to lower energies with increasing temperature slows down abo ve T-N. The experimental data are compared with a simulation of the ex citation process in a simple cubic Ising model, which gives a good qua litative and even quantitative description of the excitation process a t and above T-N.