Liquid-Phase Epitaxial Growth of 3 in Diameter Bismuth-Doped Thulium Iron Garnet Films for Magneto-Optical Applications

We report here the successful growth of a 3 in diameter magneto-optical (MO) garnet film having the composition (BiTm)₃Fe₅O₁₂ by use of the liquid-phase epitaxy (LPE) method. In these experiments, Bi₂O₃ has been used as the fluxing agent thus omitting the use of PbO, which is highly toxic and often detrimental to the quality of film growth. Films with low defect concentration, mirror-like optical surface, high Faraday rotation angle (FRA), and large thicknesses have been obtained by optimizing the flux ratio and LPE process parameters. The thicknesses of the films have been demonstrated to reach 50-60 μm for 3 in GGG substrates. The lattice parameter mismatch between Bi-doped TmIG (Bi:TmIG) film and the GGG substrate reaches a minimum resulting in optimal magnetic and MO properties at a growth rate of 0.87 μm/min. The largest FRA of 0.54°/μm corresponds to an external magnetic field of 25 Oe. The saturation magnetization (4πM_s), 48 emu/cm³, and coercivity (Hc), 2.5 Oe, of Bi:TmIG film reach respective maximum and minimum values for the growth rate 0.87 μm/min.