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arxiv: 2606.10542 · v1 · pith:Y7PFMSRSnew · submitted 2026-06-09 · ❄️ cond-mat.mtrl-sci

Probing Spin Configurations in Exchange-Coupled Magnetic Bilayers with Orthogonal Anisotropies via Anomalous Hall and Nernst Effects

Sebin Jung , Hiroki Koizumi , Hiroaki Sukegawa , Hideto Yanagihara This is my paper

Pith reviewed 2026-06-27 12:55 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords anomalous Hall effectanomalous Nernst effectexchange couplingmagnetic bilayersspin configurationsmicromagnetic simulationantiferromagnetic coupling
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0 comments X

The pith

Combining anomalous Hall and Nernst effect measurements reveals a twisted magnetic structure near the interface in antiferromagnetically coupled Fe/CoFe2O4 bilayers.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that transport measurements can access three-dimensional magnetization details in bilayers where two ferromagnetic layers with orthogonal easy axes are exchange-coupled. In the specific CoFe2O4(001)/Fe system the insulating CoFe2O4 layer isolates the signals to the conductive Fe layer, so that the anomalous Hall effect and anomalous Nernst effect together supply complementary information on the out-of-plane and in-plane spin components. Matching the measured signals against a simple micromagnetic simulation then shows that the antiferromagnetic coupling produces a nonuniform, twisted magnetization profile rather than a uniform or simple domain state near the interface.

Core claim

In a CoFe2O4(001)/Fe bilayer the insulating nature of CoFe2O4 ensures that anomalous Hall and anomalous Nernst measurements selectively probe the Fe layer; when the two effects are combined and compared with micromagnetic simulations they indicate that antiferromagnetic exchange coupling produces a twisted magnetic structure near the interface.

What carries the argument

The joint use of anomalous Hall effect (sensitive to out-of-plane magnetization) and anomalous Nernst effect (sensitive to in-plane components), interpreted via comparison with a micromagnetic model of the exchange-coupled bilayer.

If this is right

  • Electrical readout of three-dimensional spin configurations becomes possible in exchange-coupled bilayers with orthogonal anisotropies.
  • Antiferromagnetic coupling between layers with different easy axes leads to a nontrivial, depth-dependent magnetization profile.
  • The twisted structure is localized near the interface rather than extending uniformly through the Fe film.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same combined AHE-ANE approach could be applied to other insulating-ferromagnet bilayers to map interface twists without requiring neutron or x-ray probes.
  • If the twist angle can be tuned by layer thickness or temperature, the bilayer might serve as a building block for devices that rely on controlled non-collinear spin textures.
  • The method assumes the Nernst signal arises only from the in-plane magnetization component; any additional thermoelectric contributions at the interface would require separate calibration.

Load-bearing premise

The micromagnetic simulation accurately reproduces the actual interface spin arrangement without additional interfacial effects or more complex domain structures.

What would settle it

A direct observation that the measured AHE-to-ANE ratio matches the prediction for uniform magnetization throughout the Fe layer, or that the data cannot be fit by any twisted configuration in the simulation.

Figures

Figures reproduced from arXiv: 2606.10542 by Hideto Yanagihara, Hiroaki Sukegawa, Hiroki Koizumi, Sebin Jung.

Figure 1
Figure 1. Figure 1: FIG. 1. Measurement setup and transport responses of [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Transport responses of the magnetic bilayer with [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Macrospin model analysis of the magnetization [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Macrospin model calculation of the magnetization [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Interfacial effects and layered-spin model simulati [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
read the original abstract

When two ferromagnetic thin films with different magnetic easy axes are coupled via the exchange interaction, the magnetization process becomes nontrivial. In this paper, we demonstrate that three-dimensional magnetization information in such a bilayer system can be accessed electrically by combining measurements of the anomalous Hall effect (AHE) and anomalous Nernst effect (ANE). Specifically, we investigate a CoFe$_2$O$_4$(001)/Fe bilayer, where the insulating nature of CoFe$_2$O$_4$ ensures that these transport measurements selectively probe only the conductive Fe layer. By combining the AHE and ANE results and comparing them with a simple micromagnetic simulation, we probe the magnetic configuration of antiferromagnetically coupled Fe layer and suggest the emergence of a twisted magnetic structure near the interface.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 0 minor

Summary. The manuscript investigates CoFe₂O₄(001)/Fe bilayers with orthogonal anisotropies and antiferromagnetic exchange coupling. It claims that AHE (sensitive to out-of-plane magnetization) and ANE (sensitive to in-plane components) measurements, asserted to selectively probe only the conductive Fe layer because of the insulating CFO, can be combined and compared to a simple micromagnetic simulation to determine the Fe-layer magnetic configuration and indicate the presence of a twisted spin structure near the interface.

Significance. If the selective-probing assumption and the simulation comparison are robustly validated, the work would demonstrate an electrical route to three-dimensional magnetization information in exchange-coupled bilayers, which is of interest for spintronics and fundamental magnetism studies.

major comments (2)
  1. [Abstract] Abstract: The central claim that 'the insulating nature of CoFe₂O₄ ensures that these transport measurements selectively probe only the conductive Fe layer' is presented without supporting data (resistivity values, thickness dependence, or CFO-only control samples). This assumption is load-bearing; any interfacial conduction, oxygen vacancies, or pinholes would produce mixed AHE/ANE signals from both layers, rendering the micromagnetic simulation comparison for the Fe layer alone inconclusive.
  2. [Abstract] Abstract (and implied results section): No quantitative details are given on how the combined AHE+ANE data set constrains the simulation parameters or on the goodness-of-fit metrics used to identify the twisted interfacial structure. Without error bars, multiple field orientations, or explicit comparison of measured versus simulated voltage traces, the suggestion of a twisted structure remains unverified.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments. We address each major point below and will revise the manuscript to strengthen the presentation of supporting data and quantitative analysis.

read point-by-point responses

  1. Referee: The central claim that 'the insulating nature of CoFe₂O₄ ensures that these transport measurements selectively probe only the conductive Fe layer' is presented without supporting data (resistivity values, thickness dependence, or CFO-only control samples). This assumption is load-bearing; any interfacial conduction, oxygen vacancies, or pinholes would produce mixed AHE/ANE signals from both layers, rendering the micromagnetic simulation comparison for the Fe layer alone inconclusive.

    Authors: We agree that the abstract states the selective-probing claim without explicit supporting data. The manuscript relies on the established insulating character of CFO, but to address the concern we will add measured resistivity values for both layers, sample characterization details ruling out pinholes, and arguments against significant interfacial conduction or oxygen-vacancy effects. If a CFO-only control sample exists in our data set we will include it; otherwise we will note the limitation and strengthen the supporting arguments. revision: yes

  2. Referee: No quantitative details are given on how the combined AHE+ANE data set constrains the simulation parameters or on the goodness-of-fit metrics used to identify the twisted interfacial structure. Without error bars, multiple field orientations, or explicit comparison of measured versus simulated voltage traces, the suggestion of a twisted structure remains unverified.

    Authors: The manuscript compares the combined AHE and ANE data to micromagnetic simulations to suggest a twisted interfacial structure, but we acknowledge the absence of explicit quantitative metrics. In revision we will add error bars to the experimental traces, describe the simulation-parameter constraints and fitting procedure, report goodness-of-fit values (e.g., reduced chi-squared), and overlay measured versus simulated voltage traces for the multiple field orientations already present in the data set. revision: yes

Circularity Check

0 steps flagged

No circularity detected in derivation chain

full rationale

The paper states that AHE and ANE measurements selectively probe the Fe layer due to the insulating nature of CoFe2O4, then combines those experimental signals with comparison to an external simple micromagnetic simulation to infer the Fe-layer configuration and interfacial twist. No quoted step reduces by construction to a fitted parameter, self-citation chain, or self-definitional ansatz; the simulation is presented as independent, and the insulating assumption is asserted without internal derivation that loops back to the target result. The derivation chain is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only; no free parameters, axioms, or invented entities are specified in the provided text.

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Reference graph

Works this paper leans on

52 extracted references

  1. [1]

    Brodkorb and W

    W. Brodkorb and W. Haubenreisser, physica status solidi (a) 3, 333 (1970)

    1970

  2. [2]

    Yafet, Journal of Applied Physics 61, 4058 (1987)

    Y. Yafet, Journal of Applied Physics 61, 4058 (1987)

    1987

  3. [3]

    Bruno and C

    P. Bruno and C. Chappert, Phys. Rev. Lett. 67, 1602 (1991)

    1991

  4. [4]

    M. D. Stiles, Phys. Rev. B 48, 7238 (1993)

    1993

  5. [5]

    N. C. Koon, Phys. Rev. Lett. 78, 4865 (1997)

    1997

  6. [6]

    Stiles, Journal of Magnetism and Magnetic Materials 200, 322 (1999)

    M. Stiles, Journal of Magnetism and Magnetic Materials 200, 322 (1999)

    1999

  7. [7]

    C. F. Majkrzak, J. W. Cable, J. Kwo, M. Hong, D. B. McWhan, Y. Yafet, J. V. Waszczak, and C. Vettier, Phys. Rev. Lett. 56, 2700 (1986)

    1986

  8. [8]

    M. B. Salamon, S. Sinha, J. J. Rhyne, J. E. Cunningham, R. W. Erwin, J. Borchers, and C. P. Flynn, Phys. Rev. Lett. 56, 259 (1986)

    1986

  9. [9]

    T. J. Moran and I. K. Schuller, Journal of Applied Physics 79, 5109 (1996)

    1996

  10. [10]

    Nogu´ es and I

    J. Nogu´ es and I. K. Schuller, Journal of Magnetism and Magnetic Materials 192, 203 (1999)

    1999

  11. [11]

    W. E. Bailey, A. Ghosh, S. Auffret, E. Gautier, U. Ebels, F. Wilhelm, and A. Rogalev, Phys. Rev. B 86, 144403 (2012)

    2012

  12. [12]

    Surampalli, A

    A. Surampalli, A. K. Bera, R. V. Chopdekar, A. Kalitsov, L. Wan, J. Katine, D. Stewart, T. Santos, and B. Prasad, Advanced Functional Materials 34, 2408599 (2024)

    2024

  13. [13]

    Bruno, Phys

    P. Bruno, Phys. Rev. B 52, 411 (1995)

    1995

  14. [14]

    Kasuya, Progress of Theoretical Physics 16, 45 (1956)

    T. Kasuya, Progress of Theoretical Physics 16, 45 (1956)

    1956

  15. [15]

    M. T. Johnson, S. T. Purcell, N. W. E. McGee, R. Co- ehoorn, J. aan de Stegge, and W. Hoving, Phys. Rev. Lett. 68, 2688 (1992)

    1992

  16. [16]

    S. S. P. Parkin, N. More, and K. P. Roche, Phys. Rev. Lett. 64, 2304 (1990)

    1990

  17. [17]

    Olmos, H

    R. Olmos, H. Iturriaga, D. S. Blazer, S. Koohfar, K. Gandha, I. C. Nlebedim, D. P. Kumah, and S. R. Singamaneni, AIP Advances 10, 015001 (2020)

    2020

  18. [18]

    Binasch, P

    G. Binasch, P. Gr¨ unberg, F. Saurenbach, and W. Zinn, Phys. Rev. B 39, 4828 (1989)

    1989

  19. [20]

    Stobiecki, J

    T. Stobiecki, J. Kanak, J. Wrona, M. Czapkiewicz, C. G. Kim, C. O. Kim, M. Tsunoda, and M. Takahashi, physica status solidi (a) 201, 1621 (2004)

    2004

  20. [21]

    Yoshida, T

    C. Yoshida, T. Takenaga, Y. Yamazaki, H. Ue- hara, H. Noshiro, K. Tsunoda, Y. Iba, A. Hatada, M. Nakabayashi, A. Takahashi, M. Aoki, and T. Sugii, IEEE Transactions on Magnetics 50, 1 (2014)

    2014

  21. [22]

    Dieny, J

    B. Dieny, J. P. Gavigan, and J. P. Rebouillat, Journal of Physics: Condensed Matter 2, 159 (1990)

    1990

  22. [23]

    Y. C. Lee, C. T. Chao, L. C. Li, Y. W. Suen, L. Horng, T.-H. Wu, C. R. Chang, and J. C. Wu, Journal of Applied Physics 117, 17A320 (2015)

    2015

  23. [24]

    T. N. A. Nguyen, Y. Fang, V. Fallahi, N. Benatmane, S. M. Mohseni, R. K. Dumas, and J. ˚ Akerman, Applied Physics Letters 98, 172502 (2011)

    2011

  24. [25]

    T. N. A. Nguyen, R. Knut, V. Fallahi, S. Chung, Q. T. Le, S. M. Mohseni, O. Karis, S. Peredkov, R. K. Du- mas, C. W. Miller, and J. ˚ Akerman, Phys. Rev. Appl. 2, 044014 (2014)

    2014

  25. [26]

    Z. R. Nunn, C. Abert, D. Suess, and E. Girt, Science Advances 6, eabd8861 (2020). 7

    2020

  26. [27]

    Lisik, S

    J. Lisik, S. Myrtle, and E. Girt, Journal of Magnetism and Magnetic Materials 585, 171109 (2023)

    2023

  27. [28]

    P. D. Kulkarni and T. Nakatani, Applied Physics Letters 125, 162405 (2024)

    2024

  28. [29]

    Brabers, in Handbook of Magnetic Materials , Vol

    V. Brabers, in Handbook of Magnetic Materials , Vol. 8 (Elsevier, 1995) pp. 189–324

    1995

  29. [30]

    Niizeki, Y

    T. Niizeki, Y. Utsumi, R. Aoyama, H. Yanagihara, J.-i. Inoue, Y. Yamasaki, H. Nakao, K. Koike, and E. Kita, Applied Physics Letters 103, 162407 (2013)

    2013

  30. [31]

    Eskandari, S

    F. Eskandari, S. B. Porter, M. Venkatesan, P. Kameli, K. Rode, and J. M. D. Coey, Phys. Rev. Mater. 1, 074413 (2017)

    2017

  31. [32]

    Koizumi, M

    H. Koizumi, M. Hagihara, S. Kobayashi, and H. Yanagi- hara, AIP Advances 10, 015108 (2020)

    2020

  32. [33]

    Yanagihara, H

    H. Yanagihara, H. Kamita, S. Honda, J. Inoue, E. Kita, H. Itoh, and K. Mibu, Phys. Rev. B 91, 174423 (2015)

    2015

  33. [34]

    Vansteenkiste, J

    A. Vansteenkiste, J. Leliaert, M. Dvornik, M. Helsen, F. Garcia-Sanchez, and B. Van Waeyenberge, AIP Ad- vances 4, 107133 (2014)

    2014

  34. [35]

    N. D. Birell and P. C. W. Davies, Quantum Fields in Curved Space (Cambridge University Press, 1982)

    1982

  35. [36]

    Gr¨ unberg, R

    P. Gr¨ unberg, R. Schreiber, Y. Pang, M. B. Brodsky, and H. Sowers, Phys. Rev. Lett. 57, 2442 (1986)

    1986

  36. [37]

    Yu, J.-S

    P. Yu, J.-S. Lee, S. Okamoto, M. D. Rossell, M. Huijben, C.-H. Yang, Q. He, J. X. Zhang, S. Y. Yang, M. J. Lee, Q. M. Ramasse, R. Erni, Y.-H. Chu, D. A. Arena, C.-C. Kao, L. W. Martin, and R. Ramesh, Phys. Rev. Lett. 105, 027201 (2010)

    2010

  37. [38]

    Hasegawa and F

    H. Hasegawa and F. Herman, Phys. Rev. B 38, 4863 (1988)

    1988

  38. [39]

    Dieny, Journal of Magnetism and Magnetic Materials 136, 335 (1994)

    B. Dieny, Journal of Magnetism and Magnetic Materials 136, 335 (1994)

    1994

  39. [40]

    Katayama, S

    T. Katayama, S. Yuasa, J. Velev, M. Y. Zhuravlev, S. S. Jaswal, and E. Y. Tsymbal, Applied Physics Letters 89, 112503 (2006)

    2006

  40. [41]

    S. Wang, L. Yao, Y. Zhou, and S. Jiang, Phys. Rev. Appl. 24, 034054 (2025)

    2025

  41. [42]

    Ruiz-G´ omez, A

    S. Ruiz-G´ omez, A. Mandziak, L. Mart ´ ın-Garc ´ ıa, J. E. Prieto, P. Prieto, C. Munuera, M. Foerster, A. Quesada, L. Aballe, and J. de la Figuera, Applied Surface Science 600, 154045 (2022)

    2022

  42. [43]

    W. C. Cain and M. H. Kryder, Journal of Applied Physics 67, 5722 (1990), https://pubs.aip.org/aip/jap/article- pdf/67/9/5722/18634176/5722 1 online.pdf

    1990

  43. [44]

    Katsura, N

    H. Katsura, N. Nagaosa, and A. V. Balatsky, Phys. Rev. Lett. 95, 057205 (2005)

    2005

  44. [45]

    Ku´ swik, M

    P. Ku´ swik, M. Matczak, M. Kowacz, K. Szuba-Jab/suppress lo´ nski, N. Michalak, B. Szyma´ nski, A. Ehresmann, and F. Sto- biecki, Phys. Rev. B 97, 024404 (2018)

    2018

  45. [46]

    Belmeguenai, H

    M. Belmeguenai, H. Bouloussa, Y. Roussign´ e, M. S. Ga- bor, T. Petrisor, C. Tiusan, H. Yang, A. Stashkevich, and S. M. Ch´ erif, Phys. Rev. B 96, 144402 (2017)

    2017

  46. [47]

    X. Liu, C. Ren, and G. Xiao, Journal of Applied Physics 92, 4722 (2002)

    2002

  47. [48]

    D. G. Cahill, Review of Scientific Instruments 61, 802 (1990)

    1990

  48. [49]

    Kimling, A

    J. Kimling, A. Philippi-Kobs, J. Jacobsohn, H. P. Oepen, and D. G. Cahill, Phys. Rev. B 95, 184305 (2017)

    2017

  49. [50]

    He and B

    R. He and B. Sun, Journal of Applied Physics 137, 175109 (2025)

    2025

  50. [51]

    C. Y. Ho, R. W. Powell, and P. E. Liley, Journal of Phys- ical and Chemical Reference Data 1, 279 (1972)

    1972

  51. [52]

    Zhang, S

    C. Zhang, S. C. Huberman, S. Ning, J. Pelliciari, R. A. Duncan, B. Liao, S. Ojha, J. W. Freeland, K. A. Nelson, R. Comin, G. Chen, and C. A. Ross, Applied Physics Letters 113, 223105 (2018)

    2018

  52. [53]

    Jiang, B

    P. Jiang, B. Huang, and Y. K. Koh, Review of Scientific Instruments 87, 075101 (2016). 8 Supplement materials to ”Probing Spin Configurations in Exc hange-Coupled Magnetic Bilayers with Orthogonal Anisotropies via Anomalous Hall a nd Nernst Effects” I. STRUCTURAL CHARACTERIZATION FIG. S1. Crystallinity of the grown stack of sample measured with RHEED and X-r...

    2016