Direct optical excitation of two and three magnons in α-Fe2O3

Direct excitation of two and three magnons is observed in mid-infrared absorption and Raman scattering spectra of α-Fe2O3 crystals. These polarization characteristics and the spectra themselves are shown to be understood from group-theoretical point of view. The microscopic mechanism of three-magnon excitation is proposed in addition to that of well-known two-magnon excitation process.