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Emergent electric field induced by dissipative sliding dynamics of domain walls in a Weyl magnet

Abstract

The dynamic motion of topological defects in magnets induces an emergent electric field, as exemplified by the continuous flow of skyrmion vortices. However, the electrodynamics underlying this emergent field remains poorly understood. In this context, magnetic domain walls—one-dimensional topological defects with two collective modes, sliding and spin-tilt—offer a promising platform for exploration. Here we demonstrate that the dissipative motion of domain walls under oscillatory current excitation generates an emergent electric field. We image domain patterns and quantify the domain-wall length under applied magnetic fields in mesoscopic devices based on the magnetic Weyl semimetal NdAlSi. These devices exhibit exceptionally strong domain-wall scattering and a pronounced emergent electric field, as observed in the imaginary component of the complex impedance. Spin dynamics simulations reveal that domain-wall sliding dominates over spin-tilting, in which the phase delay of the domain-wall motion with respect to the driving force impacts the emergent electric field. Our findings establish domain-wall dynamics as a platform for studying emergent electromagnetic fields and motivate further investigations of the coupled motion of magnetic solitons and conduction electrons.

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Fig. 1: Schematics for a magnetic DW and its dissipative motion.
The alternative text for this image may have been generated using AI.
Fig. 2: DW resistivity and EEF in Weyl magnet NdAlSi.
The alternative text for this image may have been generated using AI.
Fig. 3: Correlation of DW length and EEF from DW motion.
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Fig. 4: Scaling of DW resistivity and the imaginary impedance.
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Data availability

All experimental data needed to reproduce the figures are available via Zenodo at https://doi.org/10.5281/zenodo.17188494 (ref. 50). Source data are provided with this paper.

Code availability

The source code used to perform the calculations described in this paper is available from the corresponding authors upon request.

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Acknowledgements

We acknowledge M. Birch, I. Belopolski, P. R. Baral, G. Chang, S. Sen, A. Ozawa, N. Nagaosa and T.-h. Arima for fruitful discussions, and the RIKEN CEMS Semiconductor Science Research Support Team for technical assistance. R.Y. was supported by the JSPS (KAKENHI Grant Nos. 22K20348, 23K13057, 24H01604 and 25K17336), the Japan Science and Technology Agency (JST) (PRESTO Grant No. JPMJPR259A), the Foundation for the Promotion of Material Science and Technology of Japan, the Yashima Environment Technology Foundation, the Yazaki Memorial Foundation for Science and Technology, and the ENEOS Tonengeneral Research/Academic Foundation. Y.F. was supported by the JST (PRESTO Grant No. JPMJPR2597). S.O. was supported by the JSPS (KAKENHI Grant Nos. 22K13998 and 23K25816) and the JST (PRESTO Grant No. JPMJPR2595). T.Y. was supported by the JSPS (KAKENHI Grant No. 24K00566) and the JST (PRESTO Grant No. JPMJPR235B). Y. Taguchi was supported by the JST (CREST Grant No. JPMJCR20T1) and the RIKEN TRIP initiative (Many-body Electron Systems and Advanced General Intelligence for Science Program). Y. Tokura was supported by the JSPS (KAKENHI Grant No. 23H05431) and the JST (CREST Grant No. JPMJCR1874). M.H. was supported by the JSPS (KAKENHI Grant Nos. 21K13877, 22H04463, 23H05431 and 24H01607), the JST (CREST Grant No. JPMJCR20T1 and FOREST Grant No. JPMJFR2238), the Fujimori Science and Technology Foundation, the New Materials and Information Foundation, the Murata Science Foundation, the Mizuho Foundation for the Promotion of Sciences, the Yamada Science Foundation, the Hattori Hokokai Foundation, the Iketani Science and Technology Foundation, the Mazda Foundation, the Casio Science Promotion Foundation, the Takayanagi Foundation, and Inamori Foundation. M.H. is also supported by the JST as part of Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE; Grant No. JPMJAP2426). M.H. is supported by the Deutsche Forschungsgemeinschaft (German Research Foundation) through Transregio (Grant No. TRR 360 - 492547816). O.A.T. acknowledges support from the Australian Research Council (Grant Nos. DP200101027 and DP240101062) and an NCMAS grant. This work is based on experiments performed at the Japan Research Reactor 3 (proposal no. 23515). This research was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the US Department of Energy. This Article has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a non-exclusive, paid-up, irrevocable, worldwide licence to publish or reproduce the published form of this Article, or allow others to do so, for US government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (www.energy.gov/doe-public-access-plan).

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Authors and Affiliations

Authors

Contributions

Y. Tokura and M.H. conceived the project. R.Y., A.K. and Y. Taguchi synthesized the bulk NdAlSi single crystal. R.Y. and Y.F. fabricated the FIB devices. R.Y. measured the MFM images and analysed the data with support from D.N. and F.S.Y. R.Y. performed the transport measurements and analysis with support from D.K., T.Y. and M.H. D.K. and O.A.T. developed the theoretical model and performed the numerical calculations. R.Y. and T.N. performed the polarized neutron scattering measurements. S.O. performed the spin model calculations. R.Y. and M.H. wrote the paper with contributions from all other co-authors.

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Correspondence to Rinsuke Yamada or Max Hirschberger.

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Extended data

Extended Data Fig. 1 Comparison of transport properties for bulk and device samples of NdAlSi.

a, Magnetoresistivity for a bulk single crystal and an FIB fabricated device (Device A). Clear quantum oscillations are observed in both cases, and the transition fields are similar, indicating little degradation during the fabrication process. b, Similar value of the Hall resistivity for a bulk single crystal and for an FIB fabricated device. This indicates that the carrier density is not changed by FIB fabrication. c,d, Oscillatory component in the magnetoresistance in the ferrimagnetic (Ferri) and ferromagnetic (FM) phases, respectively. e,f, A fast Fourier transformed spectrum of the oscillatory component with two frequencies (αS and \({\alpha }_{S}^{{\prime} }\)) and one frequency (βS) in the Ferri and FM phases, respectively.

Source data

Extended Data Fig. 2 Polarized neutron scattering experiments and estimation of the strength of the single-ion anisotropy K.

a, Measurement geometry for polarized neutron scattering. The intensities of the non-spin-flip (NSF) and spin-flip (SF) channels are related to the c-axis moment and to the moment in the ab-plane perpendicular to the Q-vector, respectively: \({I}_{{{\rm{NSF}}}}\propto {{M}^{2}}_{{{\rm{c}}}}\) and \({I}_{{{\rm{SF}}}}\propto {\mid{M}^{\perp }}_{{{\rm{in}}}}( Q)\mid^{2}\). b,c, Magnetic reflections observed at Q1/3 = (1/3 + δ1, 1/3 + δ1, 0) and Q2/3 = (2/3 + δ2, 2/3 + δ2, 0) in the incommensurate phase at 5 K, where δ1 ≠ 0 and δ2 ≠ 0. d,e, Magnetic reflections observed at Q1/3 and Q2/3 in the commensurate phase at 2.5 K, where δ1 and δ2 are nearly zero. The large ISF at Q1/3 indicates that the dominant contribution of the magnetic moment related to Q1/3 is in the ab-plane, while Mc is dominant for the Q2/3 modulation. f, Noncollinear ferrimagnetic order of NdAlSi with the in-plane magnetization component perpendicular to the Q-vector27,51. g, Definition of the spin tilt angle η of the noncollinear ferrimagnetic order (Supplementary Notes 7 and 8 and Ref. 51). h, Noncollinear ferrimagnetic order of NdAlSi in our one-dimensional spin model. i, Definition of the spin tilt angle \({\eta }^{{\prime} }\) in our spin model. j, Calculated \({\eta }^{{\prime} }\) as a function of the ratio of single-ion anisotropy K to the exchange interaction J. The experimental value of the relative angle (η ~ 20 degrees) can be reproduced by a modest value of K/J between 0.05 and 0.2.

Source data

Extended Data Fig. 3 Imaginary impedance in the device with a configuration where spin-orbit torque is forbidden.

Note that spin-orbit torque (SOT) can in principle be relevant for spin dynamics even in a bulk device of an inversion-breaking, polar material such as NdAlSi. a,b, Measurement configurations for two devices: Bc, I[110] and BIc referred to as devices A and B, respectively. In device B (panel b), the current is applied along the c-axis of NdAlSi, which corresponds to the polar axis of the crystal. The spin-orbit torque must disappear in this configuration, because the spin polarization p ~ I × P vanishes. c,d, Magnetoresistance (Re(ρxx)) of the two devices. Enhanced Re(ρxx) appears around zero field and originates from the DW resistivity e,f, Imaginary impedance (Im(ρxx)) of the two devices. The similar magnitude of Im(ρxx) between device A and B indicates that the dominant driver of the imaginary impedance in NdAlSi is likely spin-transfer torque.

Source data

Extended Data Fig. 4 Negative imaginary impedance over a wide range of current density and frequency.

Imaginary impedance multiplied by the voltage terminal distance and divided by the excitation frequency and the cross-sectional area for various frequencies and current densities (Device C). The sign of the imaginary impedance is negative over the whole regime of the parameters we explored. Our theoretical calculation shows that a negative imaginary impedance appears over a wide range of frequency and current density when Ωint/Ωext is small (area below black dotted lines in Fig. 3a). Therefore, the overall negative sign of the imaginary impedance in a wide range of parameters supports our model and the dominant sliding motion of the DW with friction.

Extended Data Fig. 5 Time dependence of the excitation, potential, and dissipation energies.

a-d, Square of the excitation current density ja.c., potential energy VX for the sliding mode X, potential energy Vϕ for the tilting mode ϕ, and time-dependent change in total energy of the spin system dEtot/dt. In this column, we focus on the limit of small intrinsic pinning frequency. e-h, Same for the case of finite intrinsic pinning frequency (Ωint = 10 kHz). The following parameters are used to perform numerical calculations (in both panels): current excitation (a.c.) frequency f = 1 kHz, extrinsic pinning frequency Ωext = 1 MHz, Gilbert damping parameter α = 0.1, and nonadiabatic damping parameter β = 0.05.

Source data

Extended Data Fig. 6 Field evolution of MFM images around zero magnetic field.

a-m, Images are taken at T = 2 K after the field-cooling (FC) at 6 T followed by the field-sweep down to 0 T for an FIB-fabricated sample with a thickness of 6 μm.

Extended Data Fig. 7 Angular dependence of the magnetic field Bd where the domain wall length goes to zero.

The inset shows the configuration of the magnetic field and current in the corresponding resistivity measurements Re(ρxx) on a mesoscopic device (Device A). The scaling of Bd with 1/ cos θ indicates that the c-component of the magnetic field plays a dominant role in the magnetization reversal process between the domains of positive and negative net magnetization.

Source data

Extended Data Fig. 8 Asymmetric imaginary impedance in the field sweep in comparison with MFM images.

a, Field dependence of the imaginary impedance measured when the magnetic field is decreasing, starting from high field (‘field down’ sweep). The three black dots correspond to the magnetic field values of three MFM images shown in panels b-d. b-d, MFM images taken at − 0.04 T, 0.0 T, and + 0.04 T with the field down condition. The asymmetric profile in the imaginary impedance is related to different domain configurations observed in the MFM images at + 0.04 T and − 0.04 T.

Source data

Supplementary information

Supplementary Information (download PDF )

Supplementary Notes 1–11, Figs. 1–4 and Tables 1–3.

Source data

Source Data Fig. 2 (download XLSX )

Measurement source data.

Source Data Fig. 3 (download XLSX )

Measurement source data.

Source Data Fig. 4 (download XLSX )

Measurement source data and data obtained by a fit to a theoretical model.

Source Data Extended Data Fig. 1 (download XLSX )

Measurement source data.

Source Data Extended Data Fig. 2 (download XLSX )

Measurement source data and data obtained by theoretical calculation.

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Data obtained by theoretical calculation.

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Measurement source data.

Source Data Extended Data Fig. 8 (download XLSX )

Measurement source data.

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Yamada, R., Kurebayashi, D., Fujishiro, Y. et al. Emergent electric field induced by dissipative sliding dynamics of domain walls in a Weyl magnet. Nat. Phys. 22, 239–244 (2026). https://doi.org/10.1038/s41567-025-03124-z

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