The effect of octahedral Fe3+and tetrahedral Fe3+dilution on the Faraday spectra of bismuth-doped iron garnets

Abstract

The Faraday spectra between 450 nm and 800 nm are reported for the series of garnets Bi_xY_3-xFe₅O₁₂, Bi_xY_3-xFe_5-yGa_y- O₁₂(y=1.0) and Bi_xY_3-xFe_5-zSc_zO₁₂(z=0.4, 0.8) and a similar series without bismuth. The component of Faraday rotation induced by the bismuth in these series has a diamagnetic wavelength dependence and indicates that a transition/transitions around 24000 cm^-1 is a major contributor to the induced component. The behaviour of the induced component with octahedral Fe³⁺ and tetragedral Fe³⁺ concentration shows that both sublattices are involved and is consistent with the observations that the band at 23200 cm^-1 is an Fe³⁺ pair transition. The strength of the induced Faraday component, in the above series, normalized to bismuth, octahedral Fe³⁺ and tetrahedral Fe³⁺ concentrations and octahedral/tetrahedral magnetic moments is a constant. The magnitude of the induced Faraday component cannot be accounted for assuming the Bi³⁺ ions split only the 23200 cm^-1 pair band in YIG.