Magneto-optical effects in Eu chalcogenides

To discuss the Faraday and Voigt effects in the Eu chalcogenides we derive a general expression for the polarizability of a system in which the important electronic transitions are from localized to itinerant orbitals. This expression is applied to a model system in which the electronic transitions take place from a 4f orbital to a 5dt_2g Wannier orbital centered at the same cell. We treat in detail the matrix elements of the electric dipole operator taking into account the many-body character of the 4f shell. The Coulomb potential of the intermediate state localized hole is included explicitely within a simple approximation. We present a numerical calculation of the frequency dependent Verdet constant and Voigt phase shift for the paramagnetic and ferromagnetic phases of EuSe. The fitting of the Verdet constant to the experimental results is fairly good and allows us to estimate the value of the integral (4f|r|5d) ? 4 × 10^?9 cm.