Preparation of magnetic oxide thin films by Sol-Gel synthesis.

In an attempt to develop a new type of magnetooptical media, we fabricated transparent iron-oxide thin films by sol-gel synthesis. A solution of ferric nitrate dissolved in ethylene glycol kept at 80°C begins to lose its fluidity and ultimately becomes a gel. The films are spin-coated on glass substrates after the solution has an appropriate viscosity, dried and then heated in air at various temperatures. Saturation magnetization 4πMs varies depending on annealing temperature and maximum 4πMs=0.74 kG was obtained by annealing at 450°C All samples have a high transmittance from visible through nearinfrared. 4πMs is greatly improved by reduction treatment in a hydrogen atmosphere at elevated temperature and increases to as large as 3 kG by annealing at 400°C but the films become semitransparent. It is noteworthy that the reduced samples successively annealed in air at 400°C recover their original high transmittance and retain the same value of 4πMs=3 kG.