Amorphous Ce1Y2Fe5O12 (Ce:YIG) thin films deposited on single crystal Si(100) and thermally oxidized Si(100) substrates by pulsed laser deposition were annealed in the temperature range of 700-1000 degrees C in air. The annealing temperature dependence of microstructure and magnetic properties of Ce:YIG films was studied using X-ray diffraction combined with vibrating sample magnetometer. The results show that single phase of polycrystalline Ce:YIG thin films can be obtained by the post-annealing of as-deposited films at the temperature of 700 degrees C. However, two steps of phase segregation of Cc:YIG occur as the post-annealing temperature increases: at first, Ce:YIG is decomposed into YIG and non-magnetic CeO2 when annealed at 800 degrees C; then YIG continues to be decomposed forming Fe2O3 when the temperature is increased up to 900 degrees C. Consequently, the saturation magnetization of Ce:YIG films decreases first and then increases with the post-annealing temperature going up, which indicates that the saturation magnetization of Ce:YIG films is mainly related to the phase composition of the films. Meanwhile, the presence of SiO2 buffer layer can significantly enhance the saturation magnetization of Ce:YIG films. (c) 2006 Elsevier B.V. All rights reserved.