Magnetic and magneto-optic properties of bismuth- and aluminum-substituted iron garnet films

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Abstract
The saturation magnetization Ms, the uniaxial anisotropy Ku, the optical absorption α, the Faraday rotation θF, and the Faraday ellipticity ψF of epitaxial garnet films of composition Y3−xBixFe5−yAlyO12 have been investigated for x≤1.34 and y≤2.22. The temperature dependence of Ms and θF at λ=633 nm have been measured in the range 4.2 K≤T≤TC. Ku, TC, θF, and ψF reveal a linear dependence on the bismuth content. The dependence of θF and ψF on the aluminum concentration shows that both sublattices are involved and indicate that the magneto-optical effects have to be ascribed to iron pair transitions. The magnitude of the growth-induced anisotropy is essentially controlled by the supercooling ΔTs and increases linearly with ΔTs. The obtainable magnetic and magneto-optical data for magneto-optical applications are discussed and compared with those of garnet films exhibiting a compensation temperature.