Effect of magnetic coupling on the magnetization reversal in arrays of magnetic nanocaps

Magnetic [Co/Pd](N) multilayers grown on assemblies of spherical polystyrene particles were used as a model system for studying the influence of magnetic coupling on the magnetization reversal by changing the size of the nanoparticles as well as the total thickness of the deposited magnetic film. The coercive field and the switching field distribution are found to be strongly dependent on the size of the nanocaps and on the total thickness of the magnetic layer, indicating a strong influence of the magnetic dipole-dipole interaction on the magnetization reversal of the entire array of nanocaps. Moreover, magnetic viscosity measurements allowed the estimation of the magnetic activation volume representing the effect of thermal activation on the switching process. It was found that the magnetic activation volume is substantially smaller compared to the volume of the nanocap and almost independent of the number of bilayers, and thus the total thickness of the nanocap, supporting an inhomogeneous magnetization reversal process.