Two and Three Magnon Excitation in α-Fe₂O₃

Abstract

Symmetry of the magnons at high symmetry points of the Brillouin zone boundary in α-Fe₂O₃ has been determined. Selection rules for the two-magnon absorption are newly derived taking acount of the four-sublattice structure of the system. Electric dipole moment proportional to the vector product of spins is introduced and is found to be able to bring about one- and three-magnon excitation.