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MA: Fachverband Magnetismus

MA 43: Focus Session: Higher-Order Magnetic Interactions – Implications in 2D and 3D Magnetism I

MA 43.9: Vortrag

Donnerstag, 19. März 2020, 12:45–13:00, HSZ 04

Role of higher-order exchange interactions for skyrmion stability — •Souvik Paul, Soumyajyoti Haldar, Stephan von Malottki, and Stefan Heinze — Institute of Theoretical Physics and Astrophysics, Christian-Albrechts-Universität zu Kiel, Germany

Magnetic skyrmions have recently become a research focus as they show promise for future magnetic memory and logic devices. One key obstacle for applications is the stability of skyrmionic bits against thermal fluctuations. The importance of Heisenberg exchange interaction, Dzyaloshinskii-Moriya interaction, magnetocrystalline anisotropy and dipole-dipole interactions in skyrmion stability has been reported. However, due to their origin from a fourth-order perturbation theory, non-Heisenberg higher-order exchange interactions (HOI) − the biquadratic, the three-site-four-spin and the four-site-four-spin interaction − have so far been neglected. Using ab-initio parametrized atomistic spin dynamics simulations for ultrathin films, we demonstrate that the HOI play an important role for skyrmion stability. We find that the effect of the first two HOI, to a large extent, can be included in the effective Heisenberg exchange constants. However, the four-site four spin interaction behaves qualitatively in a different way and has a large contribution on the energy barrier stabilizing skyrmions and antiskyrmions against annihilation. Our study opens up a new avenue to increase the stability of topological spin structures.