Paramagnetic Spin Wave Excitations by Light. I. Two-Magnon Processes

Temperature dependence of the so-called two-magnon excitation in the paramagnetic phase has been studied by using the “Equation-of-Motion Method”. The paramagnetic spin waves excited by light have been regarded as similar in nature to a quasi-collective excitation by neutrons in paramagnets in the critical region where the magnetic short-range-order is highly developed. Temperature variations of frequency shift, absorption coefficient and integrated intensity qualitatively coincide with experimental data. It was suggested that line shapes at different temperatures are similar to each other. These results assure, to some extent, our physical understanding and approach to the paramagnetic spin waves.