Ratchet motion of magnetic skyrmions driven by surface acoustic sawtooth waves
Pith reviewed 2026-05-22 23:56 UTC · model grok-4.3
The pith
Sawtooth surface acoustic waves produce net perpendicular ratchet motion of pinned magnetic skyrmions.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Sawtooth surface acoustic waves drive a ratchet motion of magnetic skyrmions in the presence of pinning centers, resulting in net motion orthogonal to the continuously applied SAW. The ratchet effect is caused by non-vanishing pinning that requires a certain strain gradient magnitude to overcome before skyrmion motion begins. Feasibility is shown through micromagnetic simulations and analytical model calculations.
What carries the argument
The asymmetric strain gradient of sawtooth surface acoustic waves interacting with pinning centers that impose a motion threshold on skyrmions.
If this is right
- Net skyrmion displacement occurs perpendicular to the propagation direction of the continuous SAW.
- The ratchet motion requires pinning centers and vanishes without them.
- A minimum strain gradient magnitude set by pinning must be exceeded for motion to start.
- Micromagnetic simulations and analytical models both confirm the directional bias.
Where Pith is reading between the lines
- The method could allow steady-state positioning of skyrmions in devices without interrupting the drive signal.
- Similar threshold-based ratchet schemes might extend to other magnetic textures such as domain walls under acoustic drive.
- Energy cost per skyrmion displacement could be compared to current-driven or field-pulse methods in future calculations.
Load-bearing premise
Pinning centers create a well-defined strain-gradient threshold that the sawtooth waveform overcomes asymmetrically to produce net motion.
What would settle it
No net orthogonal displacement occurs in micromagnetic simulations when pinning is removed or when a symmetric sinusoidal SAW replaces the sawtooth waveform.
Figures
read the original abstract
The manipulation of skyrmions by surface acoustic waves (SAW) has garnered significant interest in the field of spintronic devices. Previous studies established that skyrmions can be generated and moved by strain pulses. In this study, we propose that sawtooth-SAWs can be used to drive a ratchet motion of magnetic skyrmions in the presence of pinning centers. This results in a net motion of the skyrmions orthogonal to the continuously applied SAW. The ratchet motion is fundamentally caused by non-vanishing pinning, so that a certain strain gradient magnitude is required to overcome pinning and start skyrmion motion. We demonstrate the feasibility of our concept by micromagnetic simulations and analytical model calculations.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes that continuously applied sawtooth-shaped surface acoustic waves (SAWs) can induce ratchet motion of magnetic skyrmions when pinning centers are present. This produces a net skyrmion displacement orthogonal to the SAW propagation direction. The effect originates from the requirement that a finite strain-gradient threshold must be exceeded to overcome pinning; the asymmetric sawtooth waveform then yields unidirectional net motion. Feasibility is asserted via micromagnetic simulations and an analytical model.
Significance. If quantitatively validated, the result would supply a route to continuous, low-power SAW-based skyrmion transport that does not rely on pulsed strain. The explicit identification of pinning as the origin of the required threshold distinguishes the mechanism from prior strain-pulse work and could be relevant for skyrmion-based spintronic devices.
major comments (2)
- [Abstract / Results] Abstract and § Methods/Results: the central claim rests on the statement that micromagnetic simulations and an analytical model were performed, yet no quantitative outputs (skyrmion velocities, strain-gradient thresholds, error bars, or parameter sets) are supplied. Without these data it is impossible to judge whether the ratchet displacement is robust or merely an artifact of chosen pinning strengths.
- [Analytical model] Analytical model section: the derivation of the strain-gradient threshold and its interaction with the sawtooth waveform is not shown; the manuscript therefore provides no explicit check that the net orthogonal velocity vanishes when pinning is removed, which is required to substantiate the claim that pinning is the fundamental cause.
minor comments (2)
- [Abstract] The abstract refers to 'non-vanishing pinning' without specifying the pinning potential form or density used in the simulations.
- [Figures] Figure captions and axis labels should explicitly state the SAW amplitude, frequency, and pinning parameters so that the reported motion can be reproduced.
Simulated Author's Rebuttal
We appreciate the referee's insightful comments on our manuscript. We agree that additional quantitative details and explicit derivations are necessary to strengthen the presentation of our results. We will revise the manuscript to address these points.
read point-by-point responses
-
Referee: [Abstract / Results] Abstract and § Methods/Results: the central claim rests on the statement that micromagnetic simulations and an analytical model were performed, yet no quantitative outputs (skyrmion velocities, strain-gradient thresholds, error bars, or parameter sets) are supplied. Without these data it is impossible to judge whether the ratchet displacement is robust or merely an artifact of chosen pinning strengths.
Authors: We thank the referee for highlighting this issue. The original manuscript emphasized the conceptual demonstration via simulations and the analytical model without including specific numerical values. In the revised manuscript, we will incorporate quantitative outputs including skyrmion velocities, strain-gradient thresholds, relevant parameter sets, and error bars from the simulations. This will enable a proper evaluation of the robustness of the ratchet displacement. revision: yes
-
Referee: [Analytical model] Analytical model section: the derivation of the strain-gradient threshold and its interaction with the sawtooth waveform is not shown; the manuscript therefore provides no explicit check that the net orthogonal velocity vanishes when pinning is removed, which is required to substantiate the claim that pinning is the fundamental cause.
Authors: We agree that the explicit derivation and the check for vanishing velocity without pinning are important for substantiating the mechanism. We will add the detailed derivation of the strain-gradient threshold and its interaction with the sawtooth waveform in the revised manuscript. Furthermore, we will include simulation results demonstrating that the net orthogonal velocity is zero when pinning is absent, thereby confirming the central role of pinning. revision: yes
Circularity Check
No significant circularity; derivation self-contained
full rationale
The abstract and description indicate the ratchet motion is demonstrated via micromagnetic simulations and an analytical model, with pinning centers explicitly identified as the origin of the strain-gradient threshold. No equations, fitted parameters, or self-citation chains are referenced that reduce the claimed net orthogonal motion to a self-defined input or prior result by construction. The proposal is presented as a new concept independent of load-bearing self-references, consistent with a normal non-circular finding.
Axiom & Free-Parameter Ledger
Reference graph
Works this paper leans on
- [1]
-
[2]
M¨ uller, Magnetic skyrmions on a two-lane racetrack, New J
J. M¨ uller, Magnetic skyrmions on a two-lane racetrack, New J. Phys.19, 025002 (2017)
work page 2017
- [3]
-
[4]
B. G¨ obel and I. Mertig, Skyrmion ratchet propagation: utilizing the skyrmion Hall effect in AC racetrack storage devices, Sci. Rep.11, 3020 (2021)
work page 2021
- [5]
-
[6]
K. M. Song, J.-S. Jeong, B. Pan, X. Zhang, J. Xia, S. Cha, T.-E. Park, K. Kim, S. Finizio, J. Raabe, J. Chang, Y. Zhou, W. Zhao, W. Kang, H. Ju, and S. Woo, Skyrmion-based artificial synapses for neuromor- phic computing, Nat. Electron.3, 148 (2020)
work page 2020
- [7]
-
[8]
K. Raab, M. A. Brems, G. Beneke, T. Dohi, J. Roth¨ orl, F. Kammerbauer, J. H. Mentink, and M. Kl¨ aui, Brow- nian reservoir computing realized using geometrically confined skyrmion dynamics, Nat. Commun.13, 6982 (2022)
work page 2022
- [9]
-
[10]
T. Yokouchi, S. Sugimoto, B. Rana, S. Seki, N. Ogawa, Y. Shiomi, S. Kasai, and Y. Otani, Pattern recog- nition with neuromorphic computing using magnetic field–induced dynamics of skyrmions, Sci. Adv.8, eabq5652 (2022)
work page 2022
-
[11]
S. Li, W. Kang, Y. Huang, X. Zhang, Y. Zhou, and W. Zhao, Magnetic skyrmion-based artificial neuron de- vice, Nanotechnology28, 31LT01 (2017)
work page 2017
- [12]
- [13]
-
[14]
I. Purnama, W. L. Gan, D. W. Wong, and W. S. Lew, Guided current-induced skyrmion motion in 1D potential well, Sci. Rep.5, 10620 (2015)
work page 2015
-
[15]
R. Chen, C. Chen, L. Han, P. Liu, R. Su, W. Zhu, Y. Zhou, F. Pan, and C. Song, Ordered creation and mo- tion of skyrmions with surface acoustic wave, Nat. Com- mun.14, 4427 (2023)
work page 2023
-
[16]
T. Yokouchi, S. Sugimoto, B. Rana, S. Seki, N. Ogawa, S. Kasai, and Y. Otani, Creation of magnetic skyrmions by surface acoustic waves, Nat. Nanotechnol.15, 361 (2020)
work page 2020
-
[17]
Y. Miyazaki, T. Yokouchi, and Y. Shiomi, Trapping and manipulating skyrmions in two-dimensional films by sur- face acoustic waves, Sci. Rep.13, 1922 (2023)
work page 1922
-
[18]
Y. Liu, X. Huo, S. Xuan, and H. Yan, Manipulating movement of skyrmion by strain gradient in a nanotrack, J. Magn. Magn. Mater492, 165659 (2019)
work page 2019
-
[19]
Y. Yang, L. Zhao, D. Yi, T. Xu, Y. Chai, C. Zhang, D. Jiang, Y. Ji, D. Hou, W. Jiang, J. Tang, P. Yu, H. Wu, and T. Nan, Acoustic-driven magnetic skyrmion motion, Nat. Commun.15, 1018 (2024)
work page 2024
- [20]
- [21]
-
[22]
V. Iurchuk, J. Lindner, J. Fassbender, and A. K´ akay, Excitation of the Gyrotropic Mode in a Magnetic Vortex by Time-Varying Strain, Phys. Rev. Lett.133, 146701 (2024)
work page 2024
-
[23]
R. Moukhader, D. R. Rodrigues, A. Riveros, A. Koujok, G. Finocchio, P. Pirro, and A. Hamadeh, Injection lock- ing in DC-driven spintronic vortex oscillators via surface acoustic wave modulation, J. Appl. Phys.136, 183901 (2024)
work page 2024
-
[24]
R. L. Seeger, F. Millo, G. Soares, J.-V. Kim, A. Solignac, G. d. Loubens, and T. Devolder, Experimental observa- tion of vortex gyrotropic mode excited by surface acoustic waves, arXiv 10.48550/arXiv.2409.05998 (2024)
-
[25]
X. Gong, K. Y. Jing, J. Lu, and X. R. Wang, Skyrmion pinning by disk-shaped defects, Phys. Rev. B105, 094437 (2022)
work page 2022
- [26]
- [27]
-
[28]
F. J. R. Sch¨ ulein, E. Zallo, P. Atkinson, O. G. Schmidt, R. Trotta, A. Rastelli, A. Wixforth, and H. J. Kren- ner, Fourier synthesis of radiofrequency nanomechanical pulses with different shapes, Nat. Nanotechnol.10, 512 (2015)
work page 2015
-
[29]
M. Weiß, A. L. H¨ orner, E. Zallo, P. Atkinson, A. Rastelli, O. G. Schmidt, A. Wixforth, and H. J. Krenner, Mul- tiharmonic Frequency-Chirped Transducers for Surface- Acoustic-Wave Optomechanics, Phys. Rev. Appl9, 014004 (2018)
work page 2018
-
[30]
W. Wang, D. Song, W. Wei, P. Nan, S. Zhang, B. Ge, M. Tian, J. Zang, and H. Du, Electrical manipulation of skyrmions in a chiral magnet, Nat. Commun.13, 1593 8 (2022)
work page 2022
-
[31]
M. C. H. De Jong, B. H. M. Smit, M. J. Meijer, J. Lu- cassen, H. J. M. Swagten, B. Koopmans, and R. Lavri- jsen, Controlling magnetic skyrmion nucleation with Ga + ion irradiation, Phys. Rev. B107, 094429 (2023)
work page 2023
-
[32]
K. Fallon, S. Hughes, K. Zeissler, W. Legrand, F. Aje- jas, D. Maccariello, S. McFadzean, W. Smith, D. Mc- Grouther, S. Collin, N. Reyren, V. Cros, C. H. Mar- rows, and S. McVitie, Controlled Individual Skyrmion Nucleation at Artificial Defects Formed by Ion Irradia- tion, Small16, 1907450 (2020)
work page 2020
-
[33]
Y. Zhao, J. Wang, L. Xu, P. Yu, M. Hou, F. Meng, S. Xie, Y. Meng, R. Zhu, Z. Hou, M. Yang, J. Luo, J. Wu, Y. Xu, X. Gao, C. Feng, and G. Yu, Local Manipulation of Skyrmion Nucleation in Microscale Areas of a Thin Film with Nitrogen-Ion Implantation, ACS Appl. Mate.r Interfaces15, 15004 (2023)
work page 2023
-
[34]
X. Yu, D. Morikawa, Y. Tokunaga, M. Kubota, T. Kuru- maji, H. Oike, M. Nakamura, F. Kagawa, Y. Taguchi, T.- h. Arima, M. Kawasaki, and Y. Tokura, Current-Induced Nucleation and Annihilation of Magnetic Skyrmions at Room Temperature in a Chiral Magnet, Adv. Mater.29, 1606178 (2017)
work page 2017
- [35]
-
[36]
S. Mallick, S. Panigrahy, G. Pradhan, and S. Rohart, Current-Induced Nucleation and Motion of Skyrmions in Zero Magnetic Field, Phys. Rev. Appl.18, 064072 (2022)
work page 2022
-
[37]
Y. Quessab, J.-W. Xu, E. Cogulu, S. Finizio, J. Raabe, and A. D. Kent, Zero-Field Nucleation and Fast Motion of Skyrmions Induced by Nanosecond Current Pulses in a Ferrimagnetic Thin Film, Nano Lett.22, 6091 (2022)
work page 2022
- [38]
-
[39]
S. Finizio, K. Zeissler, S. Wintz, S. Mayr, T. Weßels, A. J. Huxtable, G. Burnell, C. H. Marrows, and J. Raabe, De- terministic Field-Free Skyrmion Nucleation at a Nano- engineered Injector Device, Nano Lett.19, 7246 (2019)
work page 2019
-
[40]
S. Rohart, and A. Thiaville, Skyrmion confinement in ultrathin film nanostructures in the presence of Dzyaloshinskii-Moriya interaction, Phys. Rev. B88, (2013)
work page 2013
-
[41]
X. S. Wang, H. Y. Yuan, and X. R. Wang, A theory on skyrmion size, Commun. Phys.1, 31 (2018)
work page 2018
- [42]
- [43]
-
[44]
D. P. Morgan,Surface Acoustic Wave Filters: With Ap- plications to Electronic Communications and Signal Pro- cessing, 2nd ed., Studies in Electrical and Electronic En- gineering Ser (Elsevier Science & Technology, San Diego, 2010)
work page 2010
- [45]
- [46]
-
[47]
R. Gruber, M. A. Brems, J. Roth¨ orl, T. Sparmann, M. Schmitt, I. Kononenko, F. Kammerbauer, M.-A. Syskaki, O. Farago, P. Virnau, and M. Kl¨ aui, 300-Times- Increased Diffusive Skyrmion Dynamics and Effective Pinning Reduction by Periodic Field Excitation, Adv. Mater35, 2208922 (2023)
work page 2023
-
[48]
A. Vansteenkiste, J. Leliaert, M. Dvornik, M. Helsen, F. Garcia-Sanchez, and B. Van Waeyenberge, The design and verification of MuMax3, AIP Adv.4, 107133 (2014)
work page 2014
-
[49]
See www.aithericon.com for Aithericon
- [50]
-
[51]
S. Woo, K. M. Song, X. Zhang, Y. Zhou, M. Ezawa, X. Liu, S. Finizio, J. Raabe, N. J. Lee, S.-I. Kim, S.-Y. Park, Y. Kim, J.-Y. Kim, D. Lee, O. Lee, J. W. Choi, B.-C. Min, H. C. Koo, and J. Chang, Current-driven dy- namics and inhibition of the skyrmion Hall effect of ferri- magnetic skyrmions in GdFeCo films, Nat. Commun.9, 959 (2018)
work page 2018
-
[52]
R. Brearton, L. A. Turnbull, J. a. T. Verezhak, G. Balakr- ishnan, P. D. Hatton, G. van der Laan, and T. Hesjedal, Deriving the skyrmion Hall angle from skyrmion lattice dynamics, Nat. Commun.12, 2723 (2021)
work page 2021
- [53]
-
[54]
S. Yang, Y. Zhao, X. Zhang, X. Xing, H. Du, X. Li, M. Mochizuki, X. Xu, J. ˚Akerman, and Y. Zhou, Fun- damentals and applications of the skyrmion Hall effect, Appl. Phys. Rev.11, 041335 (2024)
work page 2024
-
[55]
Chen, Skyrmion Hall effect, Nat
G. Chen, Skyrmion Hall effect, Nat. Phys.13, 112 (2017)
work page 2017
-
[56]
K. Litzius, I. Lemesh, B. Kr¨ uger, P. Bassirian, L. Caretta, K. Richter, F. B¨ uttner, K. Sato, O. A. Tretiakov, J. F¨ orster, R. M. Reeve, M. Weigand, I. Bykova, H. Stoll, G. Sch¨ utz, G. S. D. Beach, and M. Kl¨ aui, Skyrmion Hall effect revealed by direct time-resolved X-ray microscopy, Nat. Phys.13, 170 (2017)
work page 2017
-
[57]
See supplemental material at [url] for detailed informa- tion on the skyrmion motion over time when applying a sinusoidal and sawtooth-shaped saw to the skyrmion in a chain pinning and more realistic random grain pinning landscape
-
[58]
M. F. Ashby, Chapter 4 - Material Property Charts, in Materials Selection in Mechanical Design (Fourth Edi- tion), edited by M. F. Ashby (Butterworth-Heinemann, Oxford, 2011) pp. 57–96
work page 2011
-
[59]
V. Kavalerov, T. Fujii, and M. Inoue, Observation of highly nonlinear surface-acoustic waves on single crystal lithium–niobate plates by means of an optical sampling probe, J. Appl. Phys.87, 907 (2000)
work page 2000
-
[60]
P. Schwenke, E. Spindler, V. Vasyuchka, A. Hamadeh, P. Pirro, and M. Weiler, Zenodo (2025)
work page 2025
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.