An EPR Study of Small Magnetic Nanoparticles

Magnetic nanoparticles (MNPs) of spinel type iron oxide (of approximately 4 nm) mineralized inside the internal cavity of a mini ferritin-type protein have been investigated by means of electron magnetic resonance (EMR) spectroscopy. EMR measurements have been recorded at different temperatures in perpendicular and parallel configurations. The spectra have been interpreted using an approach based on the giant spin model. We confirm the quantum behavior of the MNPs, moreover, the thermal evolution of the spin system in terms of population of excited spin states is showed.