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

The Faraday spectra between 450 nm and 800 nm are reported for the series of garnets Bi x Y 3-x Fe 5 O 12 , Bi x Y 3-x Fe 5-y Ga y - O 12 (y=1.0) and Bi x Y 3-x Fe 5-z Sc z O 12 (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 Fe 3+ and tetragedral Fe 3+ concentration shows that both sublattices are involved and is consistent with the observations that the band at 23200 cm -1 is an Fe 3+ pair transition. The strength of the induced Faraday component, in the above series, normalized to bismuth, octahedral Fe 3+ and tetrahedral Fe 3+ concentrations and octahedral/tetrahedral magnetic moments is a constant. The magnitude of the induced Faraday component cannot be accounted for assuming the Bi 3+ ions split only the 23200 cm -1 pair band in YIG.