Room-temperature Synthesis of Magnetite Films by Ferrite Plating.

Fe3O4 (magnetite) films were successfully grown at room temperature by ferrite plating from an aqueous solution of FeCl2, utilizing Fe2+ → Fe3+ oxidation realized by adding an aqueous solution of NaNO2 + NH3 to the FeCl2 solution. Since we found that the Fe2+/Fe3O4 (solid) boundary line in the potential-pH diagram of iron shifts to the higher pH region, we increased the pH of the aqueous solution from 5.0-6.8 (at which previous plating was performed at 60°C-100°C) to 7.7-8.8. This facilitated the formation of magnetite films, which consist of single-phase magnetite, as revealed by X-ray diffraction. The magnitude of the films‘ saturation magnetization is equal to that of bulk samples. The film deposition rate was measured as a function of the pH and the concentration of NaNO2.