Three-dimensional chiral magnetization structures in FeGe nanospheres

Abstract

Skyrmions, spin spirals, and other chiral magnetization structures developing in materials with an intrinsic Dzyaloshinskii-Moriya interaction display unique properties that have been the subject of intense research in thin-film geometries. Here, we study the formation of three-dimensional chiral magnetization structures in FeGe nanospheres by means of micromagnetic finite-element simulations. In spite of the deep submicron particle size, we find a surprisingly large number of distinct equilibrium states, namely, helical, meron, skyrmion, chiral-bobber, and quasisaturation states. The distribution of these states is summarized in a phase diagram displaying the ground state as a function of the external field and particle radius. This unusual multiplicity of possible magnetization states in individual nanoparticles could be a useful feature for multistate memory devices. We also show that the magnetodipolar interaction is almost negligible in these systems, which suggests that the particles could be arranged at high density without experiencing unwanted coupling.