Crystallization and magnetic property of iron oxide nanoparticles precipitated in silica glass matrix

Crystallization and magnetic property of Fe₂O₃ nanoparticle precipitated in SiO₂ matrix was investigated. Fe₂O₃/SiO₂ nanocomposite thin film was obtained by annealing of the amorphous Fe-Si-O thin film deposited by RF-magnetron sputtering of (α-Fe₂O₃)_1-x/(SiO₂)_x composite targets. The Fe₂O₃ crystallite size increased with decreasing SiO₂ area ratio, x of the target and increasing annealing temperature. e{open}-Fe₂O₃ with the crystallite size of 20-30nm was obtained after annealing the film deposited in SiO₂ area ratio, x=0.33-0.42 at 900°C. Lower SiO₂ area ratio (x) than 0.25 and higher annealing temperature resulted in precipitation of α-Fe₂O₃ with the larger crystallite size than 40nm. In the case of SiO₂ area ratio, x≥0.50, the annealed film was amorphous and showed higher magnetization and smaller coercivity due to the precipitation of very small crystalline γ-Fe₂O₃. The e{open}-Fe₂O₃/SiO₂ composite thin film showed ferromagnetic hysteresis with coercive force of 0.14T.