Non-thermoequilibrium Bi3Fe5O12 garnet can be obtained by direct epitaxial growth onto a single-crystal garnet substrate from the vapor phase. Using a reactive ion beam sputtering technique and a target composed of 3Bi2O3 and 5Fe2O3 (molar ratio), variations in the crystalline phase with the substrate material were investigated for a variety of substrates. The substrate materials employed were fused quartz, sintered alumina, and single crystals of MgO, SrTiO3, MgAl2O4 and Gd3 (ScGa)5O12; films were prepared with these substrates at room temperature, at 480Â°C and at 540Â°C. The garnet phase did not appear on substrates other than single-crystal garnet. The thermoequilibrium phases BiFeO3 and Bi2Fe4O9 were formed only on alumina substrate. A new non-thermoequilibrium oxide with a Bi:Fe molar ratio of 3:5 was formed on the fused quartz, MgO, SrTi03 and MgAl2O4 substrates by crystallization during deposition. The oxide was found to be antiferromagnetic at room temperature.