Non uniform micromagnetic states in spheroidal magnetite nanoparticles

Abstract

Non uniform micromagnetic configurations are calculated in spheroidal magnetite nanoparticles with different semiaxis ratios, a/b = 0.5 – 2.0, using Landau-Lifshitz-Gilbert equation. We take into account a complex, combined type of particle magnetic anisotropy, associated with the presence of both cubic magneto-crystalline anisotropy and shape anisotropy of spheroidal magnetite nanoparticle. It is shown that, depending on the particle aspect ratio, there are different types of vortex states, which compete in energy with the uniform magnetization. It is also found that the single-domain diameters of magnetite nanoparticles significantly depend on the orientation of the cubic easy anisotropy axes with respect to the symmetry axis of a spheroid. The calculated single-domain diameters of spheroidal nanoparticles are in satisfactory agreement with analytical estimates.