MAGNETIC AND STRUCTURAL-PROPERTIES OF FE-FEO BILAYERS

The structural and magnetic properties of sputtered Fe/Fe-O films were studied by x-ray photoelectron spectroscopy (XPS), Rutherford backsca ttering spectroscopy, transmission electron microscopy, and supercondu cting quantum interference device. XPS studies showed the presence of FeO and Fe2O3 on the surface of as-made samples. Microstructure studie s showed a uniform nanostructure with the grain size in the range of 5 0-150 Angstrom with smaller grains corresponding to thinner films. The coercivity at 10 K was found to increase substantially with decreasin g film thickness below 60 Angstrom. A high H-c (2.7 kOe) was observed in samples with a thickness about 20 Angstrom. Magnetization curves sh owed a planar anisotropy with a shifted hysteresis loop characteristic of an exchange anisotropy between the Fe and Fe-O coating. The coerci vity was found to drop steeply with increasing temperature. This may b e attributed to the superparamagnetic behavior of the Fe-O surface lay er.