Theory of double refraction and kerr effect in BaTiO3

Abstract

The mechanism of the double refraction in the tetragonal phase of BaTiO3 is explained considering the spontaneous Kerr effect due to the local field acting on the respective ions by a microscopic way of quantum mechanics. By using the variational method the change of the electronic polarizabilities of the constituent ions due to the local field is calculated by the determination of the change of the Slater-type orbitals of the constituent ions. It is found that the birefringence obtained Δn = -0.051, which is in good agreement with the experimental value-0.054. Furthermore the coefficient d33 of the optical SHG obtained from the calculated Kerr coefficients is also calculated as -42.6 × 10-9 CGSesu, which explains well the experimental value -(42 ± 3) × 10-9 CGSesu.