Effects of interlayer exchange on collapse mechanisms and stability of magnetic skyrmions

• Published in: Physical Review B
• Main Authors: Schrautzer, Hendrik, von Malottki, Stephan, Heinze, Stefan, Bessarab, Pavel
• Other Authors: Raunvísindastofnun (HÍ), Science Institute (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Physical Society (APS) 2022
• Subjects: Eðlisfræði; exchange bias; frustrated magnetism; skyrmions; bilayer films; multilayer thin films; noncollinear magnets; Heisenberg model; Atómfræði; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/2915; https://doi.org/10.1103/PhysRevB.105.014414

Post-print / Lokaútgáfa höfundar Theoretical calculations of thermally activated decay of skyrmions in systems comprising several magnetic monolayers are presented, with a special focus on bilayer systems. Mechanisms of skyrmion collapse are identified and corresponding energy barriers and thermal collapse rates are evaluated as functions of the interlayer exchange coupling and mutual stacking of the monolayers using transition state theory and an atomistic spin Hamiltonian. In order to contrast the results to monolayer systems, the magnetic interactions within each layer are chosen so as to mimic the well-established Pd/Fe/Ir(111) system. Even bilayer systems demonstrate a rich diversity of skyrmion collapse mechanisms that sometimes coexist. For very weakly coupled layers, the skyrmions in each layer decay successively via radially symmetric shrinking. Slightly larger coupling leads to an asymmetric chimera collapse stabilized by the interlayer exchange. When the interlayer exchange coupling reaches a certain critical value, the skyrmions collapse simultaneously. Interestingly, the overall energy barrier for the skyrmion collapse does not always converge to a multiple of that for a monolayer system in the strongly coupled regime. For a certain stacking of the magnetic layers, the energy barrier as a function of the interlayer exchange coupling features a maximum and then decreases with the coupling strength in the strong coupling regime. Calculated mechanisms of skyrmion collapse are used to ultimately predict the skyrmion lifetime. Our results reveal a comprehensive picture of the thermal stability of skyrmions in magnetic multilayers and provide a perspective for realizing skyrmions with controlled properties. We gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via project no. 414321830 (HE3292/11-1) and no. 418425860 (HE3292/13-1), the Icelandic Research Fund (Grant No. 217750 and 184949), the University of Iceland Research Fund and the ...