Faraday Effect for Localized Electrons in Insulators

抄録

The formulation of the Faraday rotation in terms of dielectric constants is extended for localized electrons in insulators to include the contribution from the magnetic dipole (MD) transition in addition to the electric dipole (ED) transition. The rotation comprises four different types of terms, each of which is separated into “diamagnetic” and “paramagnetic” terms. Two of the four terms consist of absorption-type curves, and they are absent when only ED or MD transition is considered. These new terms may be important to identify the presence of the MD transition. The ω²-dependence of the rotation at ω→0 is always proven even though a special consideration is required for the case where the ground state is a Kramers doublet. Two applications are presented; the optical Faraday rotation for rare earth compounds with C_3h local symmetry; the microwave Faraday rotation for a low-lying Kramers doublet. Some typical curves of the dispersion of the rotation are given. The microwave Faraday rotation may be an effective experiment if the line width of the respective transition in the electron paramagnetic resonance is too broad to be observed.