Magnetic measurements and numerical simulations of interacting nanometer-scale particles

Magnetization processes in arrays of ferromagnetic, nanometer-scale iron pa rticles were investigated experimentally and by numerical simulations. The arrays typically consisted of several hundred, pillar-shaped particles (dia meter about 13 nm) in square or triangular arrangement. The particles were grown directly onto a thin soft-magnetic Permalloy film to enhance their in teractions. A modified boundary-element method was developed to calculate t he magnetization pattern of the particle-Permalloy heterostructures with a proper discretization of the system. The calculated magnetic behavior of th e Permalloy film, the particles, as well as the coupled heterostructure for applied fields are compared to the experimental magnetization curves. The complex magnetic behavior observed in these heterostructures (e.g., the for mation of domain walls within the Permalloy due to the particle magnetizati on) was also found numerically. These interaction effects may become releva nt for ever smaller and more dense magnetic storage media. (C) 2001 America n Institute of Physics.