Interplay between particle anisotropy and exchange interaction in Fe nanoparticle films

The magnetic properties of Fe nanoparticles films were investigated by magnetization measurements and Monte Carlo simulations. The films were produced by femtosecond pulsed laser deposition assisted by irradiation of nanoparticles with a nanosecond UV laser pulse, appropriately delayed, during their flight from the target to the substrate. The films consist of nanoparticles with a disklike shape. The initial magnetization curve exhibits a stepwise behavior, characterized by a reversible plateau followed by rapid irreversible increments. The observed behavior, induced by the peculiar nanoparticle film morphology, is the result of the competition between particle anisotropy, dipole-dipole interactions, and interparticle exchange coupling. This picture is supported by Monte Carlo simulations, satisfactorily reproducing the experimental observations.