Preparation, characterization, and magnetic properties of Fe-based alloy particles with elongated morphology

Fe-based elongated particles of about 120 x 20 nm protected with an alumina coating have been obtained by dehydration and further thermal reduction of undoped and Co-doped goethite precursors. The precursors were obtained by oxidation-precipitation of a mixture of FeSO4 and Co(NO3)(2) in the presence of NaOH and Na2CO3. Prior to the thermal treatment, the particles were coated with a homogeneous thin layer of alumina by taking advantage of the different surface charge densities of the compounds in selected pH regions. The nature and location of Co in the goethite precursors, as well as in the final metallic particles, have also been studied. Finally, the magnetic properties of the Co-doped samples have been measured and compared to that of the undoped samples in order to explain their differences. Values of the coercivity around 1200 Oe have been found in the FeCo metallic particles protected with the alumina layer.