Structure and magnetism of granular Fe-Al sub(2)O sub(3)

The structural and magnetic properties of granular Fe-Al sub(2)O sub(3) nanocomposite obtained starting from sol-gel processing are presented. Samples with nominal Fe content ranging from 20% to 62% in volume were prepared. The conversion of Fe oxides into metallic Fe was obtained by calcination at 800 degree C followed by reduction at 600 degree C for 2h in H sub(2) atmosphere. After reduction, our results indicated up to 78% alpha -Fe, preserving the mean diameter of the metallic nanoparticles between 50 and 80nm, [similar to]16% Fe oxides and [similar to]7% interstitial Fe super(2+) and substitutional Fe super(3+) cations in the Al sub(2)O sub(3) lattice. Vibrating sample magnetometry at 300 K resulted in coercivity between 400 and 630 Oe and saturation magnetization between 40 and 134 emu/g. From transport measurements, the highest magnetoresistance, close to 2% at room temperature, was observed for samples with 25% alpha -Fe and 51 vol% total Fe. copyright 2001 Elsevier Science B.V. All rights reserved.