Magnetic Interactions Effects on Magnetic Measurements for Nanoparticle Assemblies

We report on the magnetic properties of 3 nm cobalt clusters embedded in gold matrix using magnetic investigations. From the analysis of the m_FC, m_ZFC and m(H) curves, we determine precisely the Co magnetic diameter Probability Density Function (PDF) in highly diluted samples. We show that even with a 3% vol. concentrations of magnetic particles, the interactions between particles must necessarily be taken into account. For this purpose, we first determine the individual properties of particles in highly diluted samples (1%vol.). In a second step, we increase the concentration in order to retrieve the magnetic interactions signature. Exchange like interactions can be modeled by the formation of magnetic dimers, thus modifying the PDF.