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Inhomogeneous ferromagnetism mimics signatures of the topological Hall effect in SrRuO3 films
2020, Kim, Gideok, Son, K., Suyolcu, Y.E., Miao, L., Schreiber, N.J., Nair, H.P., Putzky, D., Minola, M., Christiani, G., van Aken, P.A., Shen, K.M., Schlom, D.G., Logvenov, G., Keimer, B.
Topological transport phenomena in magnetic materials are a major topic of current condensed matter research. One of the most widely studied phenomena is the topological Hall effect (THE), which is generated via spin-orbit interactions between conduction electrons and topological spin textures such as skyrmions. We report a comprehensive set of Hall effect and magnetization measurements on epitaxial films of the prototypical ferromagnetic metal SrRuO3 the magnetic and transport properties of which were systematically modulated by varying the concentration of Ru vacancies. We observe Hall effect anomalies that closely resemble signatures of the THE, but a quantitative analysis demonstrates that they result from inhomogeneities in the ferromagnetic magnetization caused by a nonrandom distribution of Ru vacancies. As such inhomogeneities are difficult to avoid and are rarely characterized independently, our results call into question the identification of topological spin textures in numerous prior transport studies of quantum materials, heterostructures, and devices. Firm conclusions regarding the presence of such textures must meet stringent conditions such as probes that couple directly to the noncollinear magnetization on the atomic scale.
Antiskyrmions and their electrical footprint in crystalline mesoscale structures of Mn1.4PtSn
2022, Winter, Moritz, Goncalves, Francisco J. T., Soldatov, Ivan, He, Yangkun, Zúñiga Céspedes, Belén E., Milde, Peter, Lenz, Kilian, Hamann, Sandra, Uhlarz, Marc, Vir, Praveen, König, Markus, Moll, Philip J. W., Schlitz, Richard, Goennenwein, Sebastian T. B., Eng, Lukas M., Schäfer, Rudolf, Wosnitza, Joachim, Felser, Claudia, Gayles, Jacob, Helm, Toni
Skyrmionic materials hold the potential for future information technologies, such as racetrack memories. Key to that advancement are systems that exhibit high tunability and scalability, with stored information being easy to read and write by means of all-electrical techniques. Topological magnetic excitations such as skyrmions and antiskyrmions, give rise to a characteristic topological Hall effect. However, the electrical detection of antiskyrmions, in both thin films and bulk samples has been challenging to date. Here, we apply magneto-optical microscopy combined with electrical transport to explore the antiskyrmion phase as it emerges in crystalline mesoscale structures of the Heusler magnet Mn1.4PtSn. We reveal the Hall signature of antiskyrmions in line with our theoretical model, comprising anomalous and topological components. We examine its dependence on the vertical device thickness, field orientation, and temperature. Our atomistic simulations and experimental anisotropy studies demonstrate the link between antiskyrmions and a complex magnetism that consists of competing ferromagnetic, antiferromagnetic, and chiral exchange interactions, not captured by micromagnetic simulations.