Dipole–Dipole Interaction in Arrays of Fe/FexOy Core/Shell Nanocubes Probed by Ferromagnetic Resonance

This paper represents a detailed theoretical study of the role of the long-range magnetic dipole-dipole interaction (DDI) evidenced by the ferromagnetic resonance (FMR) spectra for the ordered arrays of cubic nanoparticles. We show that the size of the array essentially controls the stability of the system, allowing us to suppress the intermittent low-field excitations starting from the arrays formed by 6 × 6 nanoparticles. Our numerical simulations allow us to determine the threshold inter-particle distance (around 80 ÷ 100nm), after which the DDI becomes negligible so that the FMR spectrum of the nanoparticle arrays becomes the same as the spectrum featured by a single nanoparticle. We also compare our simulations with experimental FMR-spectra of 24 Fe/Fe_xO_ynanocubes irregularly placed on a substrate.