Magnetic vortex behavior and its dynamics in nanomagnets in the presence of impurities

Using spin dynamics simulations we study and present a model for pointlike magnetic impurities in nano-magnets based on the exchange coupling between these pointlike impurities and their neighbors. We observed two possible types of impurities, acting as pinning (attractive) or scatter (repulsive) sites. A gaussian profile was observed for the interaction potential energy ranging up to two lattice parameters. Using the known values of the parameters for Permalloy-79 we have calculated the interaction energy of the vortex core with a single defect. We estimated the interaction range as approximately 10 nm. Both results agree quite well with experimental measurements. Also, we study the influence of magnetic impurities in the frequency of the gyrotropic mode in nanodisks of Permalloy-79. We observed fluctuations in the frequency which is in agreement with recent experimental results.