Size-dependent frequency bands in the ferromagnetic resonance of a Fe-nanocube

Abstract

Using full micromagnetic simulations we calculate the spectra of ferromagnetic resonance (FMR) for an iron (core-shell) nanocube and show that the FMR characteristics are strongly size dependent. For instance, for a $40$nm it is found that, in contrast to a macrospin picture, the spectrum of the iron nanocube possesses two bands centered around $0.4$T and $\approx 0.1$T. The peaks originate from the surface anisotropy induced by the strong demagnetizing fields (DMFs) of iron. Further simulations reveal that for $\approx 20$nm nanocubes the macrospin model becomes viable. Above $40$nm we find a broad band for FMR absorption. Our results point to possible interpretations of existing FMR experimental observations for the system studied here.

7 pages, 9 figures, submitted to Journal of Magnetism and Magnetic Materials