Garnet films of composition Lu3−xBixFe5−yGayO12are grown by liquid‐phase epitaxy on [111]‐oriented substrates of gadolinium gallium garnet. Faraday rotation and saturation magnetization are measured as a function of substitution levels, which range up tox=1.4 andy=1.8, respectively. Nonreciprocal propagation of the TM0is studied at a wavelength of 1.3 &mgr;m. It is shown that the difference between forward and backward propagation constants can be optimized using double layers with opposite sign of the Faraday rotation. Agreement between experiments and calculations is excellent. ©1995 American Institute of Physics.