paper

Origin of the hump anomalies in the Hall resistance loops of ultrathin SrRuO/SrIrO multilayers

arXiv:2008.09028 · doi:10.1103/PhysRevMaterials.5.014403

Abstract

The proposal that very small Néel skyrmions can form in SrRuO/SrIrO epitaxial bilayers and that the electric field-effect can be used to manipulate these skyrmions in gated devices strongly stimulated the recent research of SrRuO heterostructures. A strong interfacial Dzyaloshinskii-Moriya interaction, combined with the breaking of inversion symmetry, was considered as the driving force for the formation of skyrmions in SrRuO/SrIrO bilayers. Here, we investigated nominally symmetric heterostructures in which an ultrathin ferromagnetic SrRuO layer is sandwiched between large spin-orbit coupling SrIrO layers, for which the conditions are not favorable for the emergence of a net interfacial Dzyaloshinskii-Moriya interaction. Previously the formation of skyrmions in the asymmetric SrRuO/SrIrO bilayers was inferred from anomalous Hall resistance loops showing humplike features that resembled topological Hall effect contributions. Symmetric SrIrO/SrRuO/SrIrO trilayers do not show hump anomalies in the Hall loops. However, the anomalous Hall resistance loops of symmetric multilayers, in which the trilayer is stacked several times, do exhibit the humplike structures, similar to the asymmetric SrRuO/SrIrO bilayers. The origin of the Hall effect loop anomalies likely resides in unavoidable differences in the electronic and magnetic properties of the individual SrRuO layers rather than in the formation of skyrmions.

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