FARADAY ROTATION IN BISMUTH SUBSTITUTED IRON GARNETS

Abstract

The contribution of bismuth to the magnetooptical (MO) effects in ferromagnetic garnets is reviewed and discussed with respect to applications in the two visible and near infrared bands which correspond respectively to "perpendicular" and "parallel" optical geometries for MO devices. The temperature and Bi content dependences of the Faraday rotation are investigated at λ = 1150 and 633 nm and the influence of bismuth on the first order MO coefficients of Fe3+ ions mainly induced by electric dipole transitions are determined in the octa- and tetrahedral sites. The origin of the anomalous rotation is studied from the spectral dependence of the MO effect performed in the 0.5 - 3 eV range. The experimental spectra are fit for accurate formula which take into account all the frequency extension of a set of paramagnetic and diamagnetic transitions. It is shown that most of specific rotation in visible and near infrared originates mainly from a strong paramagnetic transition centered at 2.79 eV. These MO effects in Bi-garnet systems are compared to the high Faraday rotation induced mainly by light rare earth such as Nd, Pr, and Ce.