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The possibility for direct synthesis of fct-FePt nanoparticles of the order of 3–4 nm in diameter through the coreduction of iron and platinum ions in a polyol has been explored. We have succeeded in the synthesis of face-centered cubic structured 3–4 nm diameter FePt particles whose composition was very close to Fe50Pt50. The Fe:Pt ratio was influenced little by the molar ratios of Fe and Pt acetylacetonate dissolved in ethylene glycol. However, depending on the polyol/Pt ratio, the as-prepared samples were either superparamagnetic or ferromagnetic. The transition temperature (Tt) and magnetic properties of the as-prepared FePt were very sensitive to the reaction conditions, and the Tt varied between 593 and 893 K and the particles were ferromagnetic. The as-prepared FePt under the optimum condition had a Tt as low as 593 K and Hc as high as 1.11 kOe at an applied field of 1 T at room temperature. Furthermore, when the as-prepared FePt nanoparticles with Tt around 593 K were annealed at 673 K in H2/N2 atmosphere for an hour they transformed to the ordered fct (L10) structure with coercivity as high as 4.2 kOe at 300 K. This confirmed the lowering of Tt by the manipulation of the reaction condition alone.

X-ray photoelectron spectroscopy (XPS), ellipsometry, and cathode luminescence were utilized for characterizing oxide films formed on the surfaces of FeCo-V alloys (Permendur) that contained small amounts of aluminum via annealing under a low partial pressure of oxygen. XPS spectra showed that the oxide films were composed primarily of aluminum oxide, which was a result of preferential oxidation of aluminum on the surfaces of the alloys during annealing. The thicknesses of the oxide films were estimated from XPS depth profiles coupled with the sputtering rate of a SO2/Si film, and the thicknesses were compared with those of the oxide films measured via non-destructive ellipsometry. The thicknesses obtained from the depth profiles may have been overestimated because of a difference in sputtering rate between silicon oxide and aluminum oxide. As measured via ellipsometry, the thickness of the aluminum oxide thin film, which was less than 100 nm, increases with the aluminum content in the alloys. Wide XPS spectra from the sample surfaces with different roughness suggested that the aluminum oxide thin films were homogenously formed on the smooth surfaces, whereas metallic elements in the alloy substrates were detected on the rough surfaces. Furthermore, the electrical resistivity of the alloys with the smooth surfaces increases significantly with the aluminum content, which may be attributable to the formation of the aluminum oxide thin film. These results indicate that the addition of a small amount of aluminum and surface smoothness are important for controlling formation of the aluminum oxide thin films with high resistivity in FeCo-V alloys by annealing under a low partial pressure of oxygen.

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