Theory of Photoinduced Uniaxial Anisotropy in Silicon-Doped Yttrium Iron Garnet

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Abstract
The polarization dependence of the photodetachment cross section for Fe2+ ions on ``a'' sites in YIG:Si is shown to provide a mechanism which explains part of the photoinduced uniaxial anisotropy in this material. Using a crystal‐field theory, we have obtained quantitative predictions for the relative anisotropy in the cross section and found that a 5%–10% population imbalance between differently oriented sites is expected for light polarized along the [110] direction. We also report new experimental measurements which characterize the magnetization and the light polarization dependence of the uniaxial anisotropy. The measurements show a substantial polarization‐independent photomagnetic anneal, not included in the theory. However, the polarization‐dependent inducible anisotropy is in general accord with the proposed mechanism.