Magnetical studies on thin films of iron oxides

We have grown hematite ($\alpha $-Fe$_{2}$O$_{3})$ thin films on stainless steel and silicon dioxide (SiO$_{2})$ substrates and magnetite (Fe$_{3}$O$_{4})$ thin films on silicon substrates by RF magnetron sputtering process. Conversion Electron M\"{o}ssbauer (CEM) spectra of these films exhibit hyperfine parameter values which are characteristic of these iron oxides. Magnetization measurements parallel to the plane of the film as a function of temperature, M(T), were done at a constant field of 1 kOe to $\alpha $-Fe$_{2}$O$_{3}$ films and at 200 Oe to Fe$_{3}$O$_{4}$ films. The M(T) curve of the $\alpha $-Fe$_{2}$O$_{3}$ film showed a linear increasing of magnetization from 5 K to 160 K, related with the Morin transition. While the temperature of the Fe$_{3}$O$_{4}$ film is decreased, a sharp decrease in magnetization is observed at 123 K, associated to the Verwey transition. We carried out measurements of magnetization as a function of applied magnetic field, the loops of $\alpha $-Fe$_{2}$O$_{3}$ film exhibits hysteresis which is related to their weakly ferromagnetic behavior and the loops of the Fe$_{3}$O$_{4}$ film at 300 and 110 K show a magnetic value around 5 memu at 3 KOe in the curves.