The role of the spin-orbit coupling strength in the MO effects of magneticinsulators

It is currently admitted that the spin-orbit (SO) couplings play a determin ant role in the origin of the magneto-optical (MO) properties of magnetic m aterials. It is unambiguously confirmed that the role of SO coupling of the excited configuration is very weak and that the SO coupling of the ground configuration has a great influence on the MO properties. Furthermore, the symmetry of the magnetic ion environment is a crucial factor. However, cont rary to the theoretical results for the Kerr rotation of the transition met als Fe, Ni, Co and of MnBi, the Faraday rotation is not a linear function o f the SO coupling strength of the ground configuration.