Topical, but topological? The state of affairs with SrRuO3

Samuel Seddon¹, Peter Milde¹, Lukas Eng^1,2,

¹ TU Dresden, Institute of Applied Physics, Nöthnitzer Straße 61, 01187 Dresden, Germany
² ct.qmat: Dresden-Würzburg Cluster of Excellence—EXC 2147, TU Dresden, 01062 Dresden, Germany

Since the initial work in 2016 by Matsuno et al. [1], numerous constellations of SrRuO₃ have emerged in the literature, all with a common theme- employing various interfacial environments to attempt to stabilise topological spin textures in SrRuO₃ thin films. These attempts can be sub-divided into three groups - the introduction of a heavy metal spin-orbit coupling layer such as SrIrO₃; ultra-thin SrRuO₃ thin films on bare SrTiO₃ [2]; and the breaking of the surface/interfacial symmetry with the addition of a ferroelectric layer [3]. All the works have been motivated by the initial findings of unusual features in Hall resistivity measurements, resembling the topological Hall effect (and thus potentially Skyrmions), however the current trend in publications provide various alternative solutions to these Hall resistivity features.

Whilst it is becoming increasingly clear that the presence of Skyrmions in this material system is unlikely, it has forced a growing attention, both experimental [4] and theoretical [5], to be paid to the interpretation of topological Hall effect in thin film systems. This talk aims to provide a general update for the most recent additions to the literature, as well as focus on two recent works performed by the authors on two separate SrRuO₃ systems. The first work by Malsch et al. [6] indicates in ultra-thin SrRuO₃ thin films a multiple stage switching resultant from unit cell differences in film thickness due to step terraces. The second work by Seddon et al. [7] utilises interfacial symmetry breaking with ferroelectric PbTiO₃ to stabilise a non-topological double cycloidal whirling spin texture responsible for the resistivity features.

References

[1] Matusno et al., Science Advances, 2, 7, (2016)
[2] Qin et al., Advanced Materials, 31, 8, (2018)
[3] Wang et al., Nature Materials, 17, 12, (2018)
[4] Wysocki et al., Physical Review Materials, 4, 5, (2020)
[5] Bouaziz et al., Physical Review Letters, 126, 14, (2021)
[6] Malsch et al., ACS Applied Nano Materials, 3, 2, (2020)
[7] Seddon et al., Nature Communications, 12, 1, (2021)