Treatment effect of reducing environment on magneto-optical properties of Ca-doped Bi substituted Iron garnet films

Ca-doped Bi substituted iron garnet films (BiGdYb)3-xCaxFe5O12( ) were grown by LPE technique and the effects of treatments in reducing environment on the absorption loss α at wavelength λ=0.8μm were studied by using a N2H4.H2O solution. It turned out that (1) the α of as-grown films increases with increase of Ca content, however, it decreases remarkably after reducing treatment, (2) the α of Ca-free films does not change by reduction, and (3) the α of Ca-doped and subsequently reduced films is lower than that of as-grown Ca-free films and has a almost constant value of 430 dB/cm in the Ca concentration region x>0.03. These results were explained by considering the coexistence of Fe²⁺and Fe⁴⁺in as-grown states and their content changes due to Ca-doping and subsequent reduction. Faraday rotation coefficients of the films remained unchanged by both Ca-doping and reducing treatment. The magneto-optical figure of merit of Ca-doped films reached 12 deg/dB at λ=0.8 μm which is 1.4 times higher than that of Ca-free films.