Magnetic properties of Fe - Fe oxide particle systems.

Aerosol Fe nanoparticles in the as prepared state and embedded in a pours matrix of silica aerogel have been studied. The particles form agglomerates in which the magnetic coupling is maintained by the long-range dipolar interactions. The role of the silica medium consists in a reduction of the aggregate sizes down to pore sizes (20-100 nm) thus reducing the coercivity and remanence and enhancing the thermal fluctuation effects.