Hybrid chiral domain walls and skyrmions in magnetic multilayers (1712.05978v2)

Abstract: Noncollinear spin textures in ferromagnetic ultrathin films are currently the subject of renewed interest since the discovery of the interfacial Dzyaloshinskii-Moriya interaction (DMI). This antisymmetric exchange interaction selects a given chirality for the spin textures and allows stabilising configurations with nontrivial topology. Moreover, it has many crucial consequences on the dynamical properties of these topological structures, including chiral domain walls (DWs) and magnetic skyrmions. In the recent years the study of noncollinear spin textures has been extended from single ultrathin layers to magnetic multilayers with broken inversion symmetry. This extension of the structures in the vertical dimension allows very efficient current-induced motion and room-temperature stability for both N\'eel DWs and skyrmions. Here we show how in such multilayered systems the interlayer interactions can actually lead to more complex, hybrid chiral magnetisation arrangements. The described thickness-dependent reorientation of DWs is experimentally confirmed by studying demagnetised multilayers through circular dichroism in x-ray resonant magnetic scattering. We also demonstrate a simple yet reliable method for determining the magnitude of the DMI from static domains measurements even in the presence of these hybrid chiral structures, by taking into account the actual profile of the DWs. The advent of these novel hybrid chiral textures has far-reaching implications on how to stabilise and manipulate DWs as well as skymionic structures in magnetic multilayers.

Hybrid Chiral Domain Walls and Skyrmions in Magnetic Multilayers

The paper presented in this paper tackles the complex and fascinating dynamics of hybrid chiral magnetization configurations in magnetic multilayers driven by the Dzyaloshinskii-Moriya interaction (DMI). This interaction heralds significant potential in advancing the understanding and manipulation of chiral magnetic textures, which include Neel-type domain walls (DWs) and skyrmions.

Noncollinear Spin Textures & DMI

The DMI, often pronounced in systems with strong spin-orbit coupling, is critical in stabilizing noncollinear spin arrangements in magnetic films. Such stabilization leads to the favored formation of chiral DWs and skyrmions. The paper elucidates how, upon stacking ultrathin magnetic layers with heavy metal interfaces, the interfacial DMI can cause alterations in the profile of these configurations across the thickness of the multilayer. This demonstrates a substantial thickness-dependent reorientation of the DW chirality.

Experimental and Theoretical Approaches

The methodology used encompasses micromagnetic simulations alongside experimental verifications via circular dichroism in x-ray resonant magnetic scattering. These experiments notably confirm the predicted vertical chirality reorientation of domain walls, providing insights into how interlayer interactions foster hybrid DW structures, characterized by both Neel and Bloch components.

The research also presents an advanced method to quantify the DMI in such intricate multilayer configurations. By analyzing the domain periodicity, it is possible to derive the DMI's strength, which influences the energy and periodicity of domains, allowing one to assess the potential for spin-based applications.

Implications and Future Directions

The findings pave the way for exploring how these hybrid structures can be manipulated through current-induced effects and interfacial spin-orbit torques (SOTs). There’s a clear pathway offered for refining the control over magnetic DWs and skyrmion dynamics, suggesting potential in-memory storage technologies and logic devices that rely on the robust, energy-efficient manipulation of magnetic textures at room temperature.

The hybrid nature of these chiral textures suggests that practical implementations may require a delicate balance between layer composition and magnetic interactions. Future investigations could focus heavily on optimizing the structural parameters, including layer thickness and stacking order, to fully harness the DMI for reliable DW and skyrmion operation under practical conditions.

Conclusion

This research contributes crucially to the ongoing discourse regarding the design of efficient magnetic materials for next-gen data storage and spintronic devices. The interplay between theory and empirical evidence reinforces the complexity and richness of magnetic multilayer systems, emphasizing a nuanced understanding imperative for future exploitations of nontrivial magnetic topologies. As developments in nanofabrication and measurement techniques push the boundaries of what's achievable, the insights gleaned from this paper could catalyze breakthroughs in material science and condensed matter physics.