Structural and magnetic characterization of Fe-Al2 O3 composites

Full text. We report on the structural nd magnetic characterization f co-evaporated Fe 60%-(Al2 O3) 40% on Si (111) substrates. Co-evaporation was performed in a vacuum of 10 -7 mbar at room temperature using a dual e-beam system. The sample's composition was measured by Rutherford backscattering spectroscopy (RBS). Granular alloys near percolation limit, 60% of iron were obtained. The I-V curves show a non-ohmic behaviour for low values of V, indicating a tunnel conductivity between the Fe grains. This tunnel conductivity is responsible for the negative magneto resistance appearing in this samples. Hysteresis curves obtained using an Alternate Gradient magnetometer (AGM) show a superparamagnetic behavior. We believe that very small Fe grains are homogeneously dispersed through the Al2 O3 matrix. No evidence of Fe crystalline grains was observed by X-ray diffraction. To test the local order in the Fe grains, X-ray Absorption spectroscopy will be future at Brazilian National Synchrotron Light Laboratory (LNLS). (author)