Magnetic and magneto-optical properties of bismuth-substituted lutetium iron garnet films

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Abstract
Epitaxially grown bismuth-substituted lutetium iron garnet films of composition Lu3−xBixFe5O12 and (Lu,Y)3−xBixFe5O12 have been investigated with respect to the bismuth-induced changes of the saturation magnetization Ms, the Curie temperature TC, the growth-induced anisotropy Kug, the optical absorption α, and the Faraday rotation θF. The composition and temperature dependence of Ms and θF at λ=633 nm have been measured in the range 0≤x≤2.17 and 4.2 K≤T≤TC, respectively, revealing basically the same dependences on x as observed for bismuth-substituted yttrium and gadolinium iron garnet films. In contrast to the latter compositions, Kug turns out to be much smaller in lutetium-bismuth iron garnet films and is significantly increased by small yttrium additions. The temperature dependence of θF can be described in terms of the sublattice magnetizations using constant magneto-optical coefficients. The measured temperature dependence of Kug is compared with calculated results based on the single-ion theory.