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. ɛ-Fe2O3 with the crystallite size of 20–30 nm 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 40 nm. 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 ɛ-Fe2O3/SiO2 composite thin film showed ferromagnetic hysteresis with coercive force of 0.14 T.