Magnetically controlled insertion of cobalt ferrite nanoparticles into a porous anodic aluminum oxide (AAO) membrane.

The main idea of this paper is to incorporate and solidify magnetic nanoparticles of CoFe₂O₄ with a size less than 20 nm in a synthesized porous alumina membrane. In such a configuration, all the magnetic particles are oriented according to an external magnetic field and stay in this orientation even without a magnetic field after the solidification of the matrix. The procedure consists of three preliminary steps. First, we mixed the well-dispersed CoFe₂O₄ nanoparticles in a hexane solvent, to have a state transition from the liquid (CoFe₂O₄ nanoparticles surrounded by organic layer and dispersed in hexane) to the solid one of CoFe₂O₄. Second, we incorporate CoFe₂O₄ nanoparticles into the alumina membrane pores. Finally, a step of a heat treatment compatible with the magnetic nanoparticles is necessary to evaporate all the organic compounds. The insertion of nanoparticles has been done with the help of an external magnetic field. This work presents a new technique to synthesis a solid regular array of cobalt ferrite nanorods. After the removal of AAO membrane, cobalt ferrite nanorods can be used as a host for another material to prepare a nanocomposite material like extrinsic multiferroic. [ABSTRACT FROM AUTHOR]