Magneto-optic Kerr rotation of bismuth-substituted iron garnets in the 2–5.2-eV spectral range

Abstract

In connection with the large Faraday and Kerr rotations found previously in the compounds Bi_3−2xCa_2xFe_5−x V_xO₁₂ (CaVBIG), three series of related garnets containing bismuth have been prepared and the polar Kerr rotation spectra of polycrystalline samples of these materials have been studied. Three strong rotation peaks were observed near 2.7, 4, and 5 eV. In the first series, Y_2.2−2xBi_0.8Ca_2xFe_5−x V_xO₁₂ with x = 0−1.1, the influence of the V⁵⁺ and tetrahedral Fe³⁺ concentration on the three transitions was studied, in the second series, Y_3−xBi_xFe₅O₁₂ (x = 0−1.0), the influence of Bi³⁺ concentration, and in the third series, Y_2.0−xBi_1.0Ca_xFe_5−x Zr_xO₁₂, the influence of octahedral Fe³⁺. The transitions near 2.7 and 4 eV are strongly enhanced in proportion to the Bi³⁺ content. The transition near 2.7 eV, which is responsible for the high Faraday rotation in the visible, is proportional to the tetrahedral Fe³⁺ content. The effect of a small mixing of the oxygen −2p, tetrahedral iron 3d, and bismuth 6p electronic wave functions is discussed in order to explain the results. The large value of the Kerr rotations (1°) is of interest for magneto‐optic applications.