FARADAY ROTATION IN RARE-EARTH IRON GARNETS

The Faraday Rotation of YIG, GdIG, and TbIG has been measured at 1.15 μ as a function of temperature between 100° and 450°K. The rotation has been analysed in terms of electric and magnetic dipole contributions from the various sublattices (Fe3+ octahedral and tetrahedral, and Re 3+), and the contributions separated by a least-squares fit to magnetization data taken from published NMR results. (Both magnetic and electric contributions from an ion are proportional to the ionic magnetic moment). The electric dipole contribution from the two different Fe3+ sublattices were quite similar in YIG and GdIG, but those in TbIG showed a greater deviation. It is suggested that charge-transfer processes may account for this. The effect of a knowledge of the electric dipole contributions at 1.15 μ on published rotation results at longer wavelengths was investigated, and the assignment of the rotation entirely to magnetic-dipole effects was shown to be wrong. This affects deductions of magnetic g factors from long-wavelength rotation results. © 1969 The American Institute of Physics.