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# Topological Hall effect at above room temperature in heterostructures composed of a magnetic insulator and a heavy metal

## Abstract

Magnetic skyrmions are topologically robust nanoscale spin textures that can be manipulated with low current densities and are thus potential information carriers in future spintronic devices. Skyrmions have so far been mainly observed in metallic films, which suffer from ohmic losses and therefore high energy dissipation. Magnetic insulators could provide a more energy-efficient skyrmionic platform due to their low damping and absence of Joule heat loss. However, skyrmions have previously been observed in an insulating compound (Cu2OSeO3) only at cryogenic temperatures, where they are stabilized by a bulk Dzyaloshinskii–Moriya interaction. Here, we report the observation of the topological Hall effect—a signature of magnetic skyrmions—at above room temperature in a bilayer heterostructure composed of a magnetic insulator (thulium iron garnet, Tm3Fe5O12) in contact with a metal (Pt). The dependence of the topological Hall effect on the in-plane bias field and the thickness of the magnetic insulator suggest that the magnetic skyrmions are stabilized by the interfacial Dzyaloshinskii–Moriya interaction. By varying the temperature of the system, we can tune its magnetic anisotropy and obtain skyrmions in a large window of external magnetic field and enhanced stability of skyrmions in the easy-plane anisotropy regime.

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## Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

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## Acknowledgements

The authors thank J. Li for help with thin film preparation, C. Zheng and A. Navabi for assistance with device fabrication and Y. Liu for helpful discussions on micromagnetic simulations. Q.S. thanks P. Zhang for assistance with loop shift measurements. This work is supported partially by Spins and Heat in Nanoscale Electronic Systems (SHINES), an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award no. DE-SC0012670. The authors acknowledge support from the Army Research Office Multidisciplinary University Research Initiative (MURI) programme under grants W911NF-16-1-0472 and W911NF-15-1-10561. The authors at UCLA are also partially supported by the National Science Foundation (ECCS 1611570) and by C-SPIN and FAME, two of six centres of STARnet, a Semiconductor Research Corporation programme sponsored by MARCO and DARPA. Y.T. is supported by the US DOE, BES, under award no. DE-SC0012190.

## Author information

Q.S., G.Y. and K.L.W. conceived the idea. Q.S. carried out the transport measurements. Y.L. and C.T. grew the TmIG/Pt thin films. X.C. fabricated the Hall bar devices. S.K.K. and Q.S. performed the analytical calculations. Q.S. performed the micromagnetic simulations. All authors contributed to the discussion of the results. Q.S. and K.L.W. wrote the manuscript with help from other authors.

Correspondence to Qiming Shao or Kang L. Wang.

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### Competing interests

The authors declare no competing interests.

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## Supplementary Information

### Supplementary Information

Supplementary Notes 1–8 and Supplementary Figs. 1–15

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• #### DOI

https://doi.org/10.1038/s41928-019-0246-x