Metal-oxide films with magnetically-modulated nanoporous architectures

A magnetically-driven method for controlling nanodimensional porosity in so l-gel-derived metal-oxide films, including TiO2, Al2O3, and SnO2, coated on to ferromagnetic amorphous substrates, such as the magnetically-soft Metgla s(1) alloys, is described. On the basis of the porous structures observed d ependence on external magnetic field, a model is suggested to explain the p henomena. Under well-defined conditions it appears that the sol particles c oming out of solution, and undergoing Brownian motion, follow the magnetic field lines oriented perpendicularly to the substrate surface associated wi th the magnetic domain walls of the substrate; hence the porosity developed during solvent evaporation correlates with the magnetic domain size.