Yttrium iron garnet (YIG) thin films substituted erbium ions (Er+3) Er0.4Y2.6Fe5O12 films were prepared by a sol-gel method at different temperatures which varied from 800 to 1000°C for 2 hours in air. Magnetic and microstructural properties of the films were characterized with X-ray diffraction (XRD), the field emission scanning electron microscopy (FESEM), and vibrating sample magnetometer (VSM). The XRD patterns of the sample have only peaks of the garnet structure. The lattice constants decrease, while the particle size increases from 51 to 85？nm as the annealing temperature increases with average in thickness of 300？nm. The saturation magnetization and the coercivity of the samples increased from 26？(emu/cc) and 28？Oe for the film annealed at 800°C to 76？(emu/cc) and 45？Oe for film annealed at 1000°C, respectively. 1. Introduction The study of yttrium iron garnet (YIG) thin films is becoming more important because of properties that can be extensively used in optical communication [1], magneto-optical devices, and applied in microwave [2]. YIG is the most representative and well-known compound among the rare-earth garnets and various magnetizations can be achieved by substitution process. Thin and thick films have been produced in garnets using different methods such as liquid phase epitaxy, sputtering, chemical vapor deposition, liquid phase epitaxy, laser ablation, and sol-gel. In recent years, sol-gel methods have attracted much attention due to use of lower synthetic temperature to produce finer and more homogeneous particles. The sol-gel synthetic method has been widely used to prepare nanostructured films and can be used to systematically vary the chemical composition of target compounds over pulsed laser deposition and sputtering techniques which are also compatible with the fabrication of nanoscaled thin films. So in this study, sol-gel method is used to achieve homogeneous systems with respect to the desired metals. YIG is a ferromagnetic material and it has a cubic structure with a space group Ia3d with the general unit formula (Y3Fe5O12) [3]. The magnetic ions are distributed over three crystallographic sites with sublattice magnetization Ma [octahedral site, 16 Fe3+ ions in a], Md (tetrahedral site, 24 Fe3+ ions in d), and Mc {dodecahedral site, 24 Y3+ ions in c}. Ionic distribution in garnet is represented as {Y33+} [Fe23+] (Fe33+) . The interaction between the Fe3+ ions in [a] and (d) sites is strongly antiferromagnetic due to strong superexchange interaction. The magnetic moment of the rare-earth ions in the {c} sublattice couples
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