Magnetic Studies of Iron Oxide Nanoparticles Encapsulated within Nanostructured Silicon

In the frame of this work the structural and magnetic characterization of encapsulated iron oxide nanoparticles within a nanostructured silicon host is discussed. Two approaches are depicted, one to infiltrate readily synthesized Fe₃O₄ particles into the pores and second to grow iron oxide inside the pores out of an ethanolic iron salt solution. Beside the particle size dependent investigations, a key point of the presentation is the optimization of the system with respect to the desired magnetic properties (magnetic moment as high as possible, blocking temperature below room temperature) which are controlled by the filling parameters as well as by the morphology of the host. The readily synthesized particles are coated with oleic acid for stabilization and to avoid agglomeration and it also prevents magnetic exchange coupling. Dipolar coupling takes place dependent on the particle size and their distance among each other. The chemical growth of iron oxide strongly depends on the electrolyte composition as well as on the applied potentiostatic conditions. Results gained from SEM show that the grown iron oxide forms elongated structures instead of small nanoparticles. But temperature dependent magnetization measurements exhibit a blocking temperature around 35 K which indicates superparamagnetic behavior. An explanation can be given by deposits consisting of weakly interacting grains. All investigated composite systems exhibit a blocking temperature far below room temperature and due to the fact that all utilized materials are biocompatible the presented systems are promising for using as vehicle in biomedicine.