THEORY OF ABSORPTION AND SCATTERING OF LIGHT BY MAGNETIC CRYSTALS

Theories of absorption and scattering of light due to electric origins by magnetic crystals are surveyed. Electric dipole moments associated with ionic spins are discussed from symmetry point of view. Two-magnon absorptions are treated by using this spin-dependent electric dipole moment. Relative importance of various possible mechanisms giving rise to this moment are discussed. Light scattering by spin systems is treated by using the spin-dependent electric polarizability and a general expression is given for the scattering intensity. Symmetry properties and microscopic mechanisms of this polarizability are discussed systematically. One- and two-magnon scatterings as well as critical scatterings by spin systems are discussed in terms of this theory. Discussions are also extended briefly to the case of magnon-phonon absorption and the magnon sidebands or the magnon-exciton absorptions. © 1968 The American Institute of Physics.