iAFMskyrmions - Intrinsic antiferromagnetic skyrmions from first-principles: stabilization, interaction with defects and efficient detection

• Applicant: Professor Dr. Samir Lounis
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462676712

Ferromagnetic (FM) skyrmions have been discovered in a plethora of materials. Their use as future bits for information technology is hindered by their complex interaction with defects, the presence of stray fields, which limit their miniaturization, and the difficulty to control their trajectory due to the skyrmion Hall effect. These issues are expected to resolve in antiferromagnetic (AFM) skyrmions, which offer several advantages although being not-trivial to detect. So far these have been stabilized in synthetic AFM structures, i.e. multilayers hosting FM skyrmions, which couple antiferromagnetically through a non-magnetic spacer. In this proposal, we aim at the first-principles prediction of intrinsic AFM skyrmions emerging in thin films. Our preliminary work already shows the possibility of stabilizing sub-10 nm AFM skyrmions and other topological spin-textures with the right choice of elements. Hinging on density functional theory (DFT), time-dependent DFT, and multiple-scattering concepts, we plan systematic first-principles investigations of diverse combinations of materials and explore various knobs triggering complex AFM topological spin-textures focusing on: (i) quantum and thermal fluctuations, which we expect to be important in antiferromagnets; (ii) high-order multi-spin chiral interactions that we recently unveiled; (iii) detection protocols based on chiral orbital magnetism, spin-mixing magnetoresistance, and new mechanisms based on multi-site multi-spin interactions; (iv) systematic cataloging of AFMskyrmion-defect interactions and the underlying electronic mechanisms. Aiming at the identification of universal patterns, we conjecture that defect-engineering (controlled placement of selected types of defects) is useful for efficient detection, characterization, and manipulation of AFM skyrmions. We plan collaborations with the Würzburg group (Bode) having the goal of prospecting AFM skyrmions with STM measurements, with MPI-Halle (Parkin) on various aspects of skyrmions and antiskyrmions, with TUM (Back) on dynamics of skyrmions and with Konstanz/Mainz groups (Nowak/Levente/Kläui) on first-principles description of AFM spin-textures.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2137: Skyrmionics: Topological Spin Phenomena in Real-Space for Applications
• International Connection: Iceland
• Co-Investigator: Imara Lima Fernandes, Ph.D.
• Cooperation Partner: Professor Dr. Pavel Bessarab