Skyrmions and antiskyrmions in monoaxial chiral magnets (2305.13003v1)

Abstract: We show that competition between local interactions in monoaxial chiral magnets provides the stability of two-dimensional (2D) solitons with identical energies but opposite topological charges. These skyrmions and antiskyrmions represent metastable states in a wide range of parameters above the transition into the saturated ferromagnetic phase. The symmetry of the underlying micromagnetic functional gives rise to soliton zero modes allowing efficient control of their translational movement by the frequency of the circulating external magnetic field. We also discuss the role of demagnetizing fields in the energy balance between skyrmion and antiskyrmion and in their stability.

• The paper demonstrates that skyrmions and antiskyrmions in monoaxial chiral magnets share identical energy levels when demagnetizing fields are neglected.
• It reveals that the interplay among Heisenberg exchange, DMI, and Zeeman terms predominantly governs soliton stability over demagnetizing effects.
• 3D simulations show that external magnetic fields can drive skyrmions with precise translational control, suggesting potential for spintronic applications.

Analysis of Skyrmions and Antiskyrmions in Monoaxial Chiral Magnets

The article by Kuchkin and Kiselev presents a comprehensive paper on the stability and dynamics of skyrmions and antiskyrmions in monoaxial chiral magnets. The focus lies on exploring the conditions under which these two-dimensional (2D) solitons can exist as metastable states and the effects of demagnetizing fields on their stability and dynamics.

Key Findings and Contributions

The paper identifies that in monoaxial chiral magnets, the energy balance between skyrmions and antiskyrmions is driven by the competition between local interaction terms, including the Heisenberg exchange, Dzyaloshinskii-Moriya interaction (DMI), and Zeeman energy terms. This competitive interaction results in the stability of solitons with identical energy but opposite topological charges in a large parameter space above the phase transition to a saturated ferromagnetic state.

Several noteworthy outcomes are outlined:

1. Symmetrical Energy Behavior: In monoaxial systems, the energies of skyrmions and antiskyrmions are shown to be identical when demagnetizing fields are neglected. This symmetry stems from the form of the micromagnetic functional, which is invariant under certain transformations.
2. Demagnetizing Field Influence: Although demagnetizing fields slightly favor the stability of skyrmions over antiskyrmions, the primary mechanism for soliton stability remains the interplay among the Heisenberg exchange, DMI, and Zeeman terms. This challenges previously held assumptions regarding the role of demagnetizing fields in these systems.
3. Dynamic Properties: A notable contribution of this work is the paper of dynamic properties of skyrmions, detailing how these solitons can be effectively driven by external magnetic fields. Particularly, under a magnetic field circulating orthogonally to a crystal's principal axis, skyrmions display a consistent translational movement, a behavior that can be precisely controlled by field frequency.
4. 3D Simulations: Extending the theoretical results to three-dimensional (3D) settings, the paper simulates skyrmion and antiskyrmion behavior in finite thickness plates. This includes calculations that take into account demagnetizing fields, reinforcing the general applicability of the findings.

Implications and Future Directions

The implications of this research are significant both practically and theoretically. In applied magnetism and information technology, understanding skyrmion dynamics can lead to advancements in data storage and spintronic devices, where these topological solitons are potential carriers of information due to their stability and controlled motion. The findings suggest possibilities for manipulating skyrmion dynamics via external fields, leading to new control strategies in functional material design.

From a theoretical standpoint, the paper challenges conventional views of monoaxial magnetic systems and provides a model to explore skyrmion dynamics beyond traditional chiral or isotropic magnets. This opens new pathways for simulating and realizing skyrmion behaviors in novel magnetic materials. Further research could extend these results to other classes of magnets with varying anisotropy and explore field-driven dynamics in different geometric constraints.

In summary, this paper advances the understanding of skyrmion and antiskyrmion stability and dynamics in monoaxial chiral magnets, presenting a model applicable to both 2D and 3D structures. The work lays a foundation for both experimental and theoretical exploration of solitonic behaviors in unconventional magnetic materials, offering insights valuable for future explorations in condensed matter physics and material science.