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Unconventional unidirectional magnetoresistance in heterostructures of a topological semimetal and a ferromagnet

Nature Materials volume 24, pages 1049–1057 (2025)Cite this article

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Abstract

Unidirectional magnetoresistance (UMR) in a bilayer heterostructure, consisting of a spin-source material and a magnetic layer, refers to a change in the longitudinal resistance on the reversal of magnetization and originates from the interaction of non-equilibrium spin accumulation and magnetization at the interface. Since the spin polarization of an electric-field-induced non-equilibrium spin accumulation in conventional spin-source materials is restricted to be in the film plane, the ensuing UMR can only respond to the in-plane component of magnetization. However, magnets with perpendicular magnetic anisotropy are highly desired for magnetic memory and spin-logic devices, whereas the electrical read-out of perpendicular magnetic anisotropy magnets through UMR is critically missing. Here we report the discovery of an unconventional UMR in the heterostructures of a topological semimetal (WTe2) and a perpendicular magnetic anisotropy ferromagnetic insulator (Cr2Ge2Te6), which allows to electrically read the up and down magnetic states of the Cr2Ge2Te6 layer through longitudinal resistance measurements.

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Fig. 1: WTe2–CGT devices and their characterization.
Fig. 2: AHE in WTe2–CGT devices.
Fig. 3: Unconventional UMR in WTe2–CGT devices.
Fig. 4: Absence of unconventional UMR in control device.
Fig. 5: Theoretical modelling of UMR and AHE.

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Data availability

All the data supporting the findings of this study are available in the Article and its Supplementary Information. Further information is available from the corresponding author on reasonable request.

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Acknowledgements

S.S. acknowledges financial support from the National Science Foundation (NSF) through grant no. ECCS-2208057; US Office of Naval Research under award no. N00014-23-1-2751; and the Center for Emergent Materials at The Ohio State University, an NSF MRSEC, through award no. DMR-2011876. S.S. also acknowledges financial support from the NSF CAREER Award through grant no. ECCS-2339723. J.K. acknowledges financial support from the US Office of Naval Research under award no. N00014-23-1-2751; the Center for Emergent Materials at The Ohio State University, an NSF MRSEC, through award no. DMR-2011876; and the US Department of Energy, Office of Science, Office of Basic Sciences, through award no. DE-SC0020323. J.K. also acknowledges financial support from the NSF CAREER Award under grant no. DMR-2339309. J.T. and R.C. are supported by the Air Force Office of Scientific Research under grant FA9550-19-1-0307. J.Y. acknowledges support from the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. D.G.M. acknowledges support from the Gordon and Betty Moore Foundation’s EPiQS Initiative through grant no. GBMF9069. J.H. acknowledges financial support from the Center for Emergent Materials, an NSF MRSEC, through award no. DMR-2011876. Electron microscopy was performed at the Center for Electron Microscopy and Analysis at The Ohio State University. J.H.E. acknowledges support for the hBN crystal growth from the US Office of Naval Research under award no. N00014-22-1-2582. K.W. and T.T. acknowledge support from the JSPS KAKENHI (grant nos. 21H05233 and 23H02052) and World Premier International Research Center Initiative (WPI), MEXT, Japan. We also thank Ryan Muzzio for his help to prepare the schematic of the WTe2 crystal structure shown in Fig. 1.

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Authors and Affiliations

  1. Department of Physics, Carnegie Mellon University, Pittsburgh, PA, USA

    I-Hsuan Kao, Sean Yuan, Jyoti Katoch & Simranjeet Singh

  2. Department of Physics and Astronomy, University of California, Riverside, CA, USA

    Junyu Tang & Ran Cheng

  3. Department of Materials Science and Engineering, The Ohio State University, Columbus, OH, USA

    Gabriel Calderon Ortiz, Menglin Zhu & Jinwoo Hwang

  4. Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, OH, USA

    Rahul Rao

  5. Tim Taylor Department of Chemical Engineering, Kansas State University, Manhattan, KS, USA

    Jiahan Li & James H. Edgar

  6. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA

    Jiaqiang Yan & David G. Mandrus

  7. Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, USA

    Jiaqiang Yan & David G. Mandrus

  8. Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan

    Kenji Watanabe

  9. Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan

    Takashi Taniguchi

  10. Department of Electrical and Computer Engineering, University of California, Riverside, CA, USA

    Ran Cheng

  11. Department of Material Science and Engineering, University of California, Riverside, CA, USA

    Ran Cheng

Authors
  1. I-Hsuan Kao
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Contributions

S.S. and J.K. supervised the research. I.-H.K. prepared the devices and performed the experiments with assistance from S.Y. J.T. and R.C. performed the theoretical and numerical calculations. G.C.O., M.Z. and J.H. performed the STEM measurements. R.R. carried out the polarized Raman measurements. J.Y. and D.G.M. provided the bulk crystals of WTe2. J.L., J.H.E., K.W. and T.T. provided the bulk hBN crystals. All authors contributed to writing the manuscript.

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Correspondence to Simranjeet Singh.

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Nature Materials thanks Can Onur Avci and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Notes 1–12, Figs. 1–23 and Tables 1 and 2.

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Kao, IH., Tang, J., Ortiz, G.C. et al. Unconventional unidirectional magnetoresistance in heterostructures of a topological semimetal and a ferromagnet. Nat. Mater. 24, 1049–1057 (2025). https://doi.org/10.1038/s41563-025-02175-0

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