Exploration of nontrivial topological domain structures in the equilibrium state of magnetic nanodisks

Abstract

Topological magnetic domains exhibit many fascinating features and great potential in information storage and spintronics owing to their unique spin textures. In order to investigate the topological properties of the domain structures, the spontaneous evolutions of magnetic moments are evaluated by using Landau–Lifshitz–Gilbert equation. The equilibrium phase diagrams of the system with randomly, radial and axial distributed initial magnetic moments have been studied in detail. Simulation results show that the changes of quality factor (Q) and aspect ratio (T/D) lead to great differences in magnetization process under different initial magnetization states. Vortex, biskyrmion, skyrmion and bubble are formed as the value of Q gradually increases from 0 to 1. The system with Q 1.0 are arranged along the easy axis. When Q and T/D are in the range of 0.6 ~ 0.8 and 0.10 ~ 0.16, respectively, it is conducive to the formation of nontrivial topological domain. Biskyrmion is spontaneously formed in the system of Q = 0.6 and T/D = 0.12, proving that skyrmion-like domain can be generated in the absence of Dzyaloshinskii–Moriya interaction or external field.