The novel Bi-substituted rare-earth iron garnet films were grown by the modified liquid phase epitaxy (LPE) technique for use as a 45°Faraday rotator in optical isolators.First,single crystals of Y3Fe5O12 (YIG),with a lattice constant of 1.237 8 nm,were grown by means of the Czochralski method.Using the seed crystal of YIG instead of the conventional non-magnetic garnet of Gd3Ga5O12(GGG) as a substrate,a film of BiYbIG was grown by means of the LPE method from Bi2O3-B2O3fluxes.The structural,magnetic and magneto-optical properties of BiYbIG LPE film/YIG crystal composite have been investigated using directional X- ray diffraction (XRD),electron probe microanalysis (EPMA),vibrating sample magnetometer (VMS) and near-infrared transmission spectrometry.The saturation magnetization 4πMshas been estimated to be about 1.2×106 A/m.The Faraday rotation spectrum was measured by the method of rotating analyzer ellipsometry (RAE) with the wavelength varied from 800 nm to 1 700 nm.The resultant Bi0.37Yb2.63Fe5O12LPE film/YIG crystal composite showed an increased Faraday rotation coefficient due to doping Bi3+ions into the dodecahedral sites of the magnetic garnet without increasing absorption loss,therefore a good magneto-optic figure of merit,defined by the ratio of Faraday rotation and optical absorption loss,has been achieved of 21.5 and 30.2 (°)/dB at 1 300 and 1 550 nm wavelengths respectively and room temperature. Since Yb3+and Y3+ions provide the opposite contribution to the wideband and temperature characteristics of Faraday rotation, the values of Faraday rotation wavelength and temperature coefficients were reduced to 0.06 %/nm and 0.007 (°)/℃at 1 550 nm wavelength, respectively.