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

Abstract

Epitaxially grown bismuth-substituted lutetium iron garnet films of composition ${\mathrm{Lu}}_{3\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Bi}}_{\mathrm{x}}$${\mathrm{Fe}}_{5}$${\mathrm{O}}_{12}$ and (Lu,Y${)}_{3\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Bi}}_{\mathrm{x}}$${\mathrm{Fe}}_{5}$${\mathrm{O}}_{12}$ have been investigated with respect to the bismuth-induced changes of the saturation magnetization ${M}_{s}$, the Curie temperature ${T}_{C}$, the growth-induced anisotropy ${K}_{u}^{g}$, the optical absorption \ensuremath{\alpha}, and the Faraday rotation ${\ensuremath{\theta}}_{F}$. The composition and temperature dependence of ${M}_{s}$ and ${\ensuremath{\theta}}_{F}$ at \ensuremath{\lambda}=633 nm have been measured in the range 0\ensuremath{\le}x\ensuremath{\le}2.17 and 4.2 K\ensuremath{\le}T\ensuremath{\le}${T}_{C}$, 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, ${K}_{u}^{g}$ turns out to be much smaller in lutetium-bismuth iron garnet films and is significantly increased by small yttrium additions. The temperature dependence of ${\ensuremath{\theta}}_{F}$ can be described in terms of the sublattice magnetizations using constant magneto-optical coefficients. The measured temperature dependence of ${K}_{u}^{g}$ is compared with calculated results based on the single-ion theory.