Antiskyrmions on surfaces by anisotropic Dzyaloshinskii-Moriya interactions

• Applicant: Dr. Jeison Fischer
• Subject Area: Experimental Condensed Matter Physics ; Synthesis and Properties of Functional Materials
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462692705

The physics behind the magnetic swirling topological objects, referred as skyrmions, has received a lot of scrutiny. The relevance for potential new data storage devices drives the interest. Initially at the sidelines, antiskyrmions did not receive the same attention as skyrmions. Both only differ in the way the spins rotate within the magnetic object, while in skyrmions all the spins rotate coherently in all direction, in antiskyrmions the rotation is strongly direction dependent and contains four different chiralities (multichirality). Iniatially, fundamental studies have shown that a clear difference in formation energy exists, and that skyrmions are much more stable than antiskyrmions in bulk chiral magnets. In bulk solids the possibility of antiskyrmions was finally accessed in Heusler materials containing D2d symmetry, however, the case for thin films was never made. Given that thin films are more compatible with technological developments and the scientific interest in understanding the issue of stabilization of antiskyrmions. The main objective of the research within this proposal is to explore and investigate non-collinear spin textures on fcc(110) surfaces with the goal of realizing antiskyrmions arising from interface effects in ultrathin films. The strategy that will be employed involves the use of substrates containing C2v symmetry, which is a lower symmetry than the typical ones used so far (C3v and C4v). Here, the reduced symmetry leads to an anisotropic Dzyaloshinskii-Moriya interaction (DMI). The breaking of rotation symmetry of the DMI vectors has been predicted to lead to the formation of antiskyrmions, because of the multichirality that is introduced by the anisotropic DMI. Furthermore, we will exploit the adsorption of molecular overlayer (H, O, or graphene) in order to fine tune the magnetic interactions (DMI and exchange) that stabilize the antiskyrmion. Beyond the observation of antiskyrmion particular focus will be given to understand the origin and the driving forces behind its formation. The task of understanding the interactions involved will be carried out in close collaboration with the FZ-Jülich (S. Blügel). This proposal focuses on spin-polarized scanning tunneling microscopy (STM), which allows full characterization of non-collinear spin textures down to the atomic level. These measurements will be carried out at low temperatures from 400 mK – 30 K and under vector magnetic field of up 2 T and up to 9 T (out-of-plane).

• DFG Programme: Priority Programmes
• Subproject of: SPP 2137: Skyrmionics: Topological Spin Phenomena in Real-Space for Applications