Hidden magnetic phases in i-MAX compounds

Ariel Maniv; Arneil P. Reyes; Asaf Pesach; Daniel Potashnikov; Dror Yahav; El'ad N. Caspi; Eran Maniv; Johanna Rosen; Quanzheng Tao

REVIEW 4 major objections 5 minor 1 cited by

Hidden magnetic phases in i-MAX compounds

T0 review · 4 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read A high-field canted antiferromagnetic phase in i-MAX compounds appears as the rare-earth element is made heavier, with ordering temperatures that rise with applied field.

desk verdict New high-field phase in i-MAX magnets is likely real; 'canted AFM' label needs backup from neutron diffraction or NMR simulation. read the letter →

arxiv 2412.02418 v1 pith:2SUCMGSZ submitted 2024-12-03 cond-mat.str-el

Dror Yahav , Ariel Maniv , Daniel Potashnikov , Asaf Pesach , El'ad N. Caspi , Arneil P. Reyes , Quanzheng Tao , Johanna Rosen

show 1 more author

Eran Maniv

This is my paper · ORCID

classification cond-mat.str-el PACS 75.30.Kz76.60.-k75.50.Ee

keywords i-MAXcompoundscantedantiferromagnetismhigh-fieldmagnetismAl-27NMRACsusceptibilitymagneticphasediagramrare-earth(Mo2/3RE1/3)2AlC

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

i-MAX compounds are layered materials in which two metal species order within the M planes; here the authors study (Mo2/3RE1/3)2AlC with RE = Gd, Dy, Ho, Er. Using AC susceptibility and Al-27 NMR, they identify a magnetic phase that appears only at high field and whose ordering temperature increases as the field is raised, the opposite of the usual suppression of magnetic order by a field. The phase grows in field-temperature space as the rare-earth element becomes heavier, until for Er it nearly replaces the zero-field magnetic state. The authors interpret the NMR line shape as evidence of a canted antiferromagnet with a growing ferromagnetic component, and they propose that the zero-field state is a frustrated antiferromagnetic spin-density wave that converts to this canted structure under field.

What carries the argument

The load-bearing probe is field-swept Al-27 NMR, displayed against the rescaled field $H_N = (\omega_0/\gamma H)-1$, which brings out the local hyperfine field distribution. A symmetric double-peak line shape is used as the fingerprint of a canted antiferromagnetic state, in which spins are tilted with a net component along the applied field, following the identification in the related compound [19]. AC susceptibility supplies the thermodynamic phase boundaries by locating the maxima of $\chi'(T)$, and the combination of the two probes maps the H–T phase diagrams and traces how the high-field phase grows with rare-earth substitution.

What would settle it

A high-field neutron diffraction experiment on Ho-i at H = 13–15 T and T = 4–30 K, looking for the coexistence of antiferromagnetic and ferromagnetic Bragg peaks, would settle whether the high-field phase is canted AFM; observing a purely collinear structure or no antiferromagnetic signal would falsify the central claim.

Watch

Extended reading notes

Core claim

For the heavier rare-earth members of the series, the paper establishes a high-field phase distinct from the low-field antiferromagnetic states known from earlier work. The phase appears as a broad anomaly in AC susceptibility whose peak temperature rises with applied field up to at least 9 T for Dy-i, Ho-i, and Er-i, and as a negatively shifted double-peak in Al-27 NMR field sweeps. The authors take the double-peak shape, following the fingerprint established for a related compound, to indicate canted antiferromagnetic order with a significant ferromagnetic component; in Ho-i the double-peak persists up to 30 K and fields of 15–17 T. As RE changes from Gd through Dy and Ho to Er, the high-field phase occupies progressively more of the H–T diagram, the low-field phase shrinks, and in Er-i the zero-field transition is suppressed already by 0.04 T while the high-field phase dominates above about 2 T. The conclusion is a competition between magnetic states in which increasing field stabilizes the canted phase, likely through its ferromagnetic component along the a-axis.

Load-bearing premise

The central assumption is that every AC susceptibility anomaly marks a true magnetic phase transition and that the double-peaked NMR signal is a reliable fingerprint of a canted antiferromagnetic state—spins tilted partly along the field—with no independent high-field neutron diffraction or spectral simulation to confirm the spin structure.

Editorial extensions

If this is right

For Dy-i, Ho-i, and Er-i, the high-field phase's transition temperature rises with applied field up to at least 9 T, marking a magnetic order that is stabilized rather than destroyed by field.
The phase survives to fields of at least 15–17 T in Ho-i, as seen in Al-27 NMR, so the canted state is a robust high-field ground state of the series.
As the rare-earth atomic number increases, the low-field antiferromagnetic phase shrinks and the high-field canted phase expands; in Er-i the zero-field transition disappears already by 0.04 T and the high-field phase dominates above about 2 T.
The authors' proposed picture—zero-field antiferromagnetic spin-density wave converting under field to a canted AFM with a field-aligned ferromagnetic component along the a-axis—gives a specific structure to be tested by high-field neutron diffraction.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

If neutron diffraction confirms the canted structure, the field-stabilized ferromagnetic component could make exfoliated MXene flakes derived from these i-MAX parents magnetically addressable at modest fields, a property relevant for two-dimensional magnetism.
The systematic trend across Gd, Dy, Ho, Er suggests lanthanide contraction tunes the competition between phases; a testable extension is that even heavier rare-earth substitutions or diluted solid solutions would move the high-field phase to lower applied fields, possibly to zero field.
The NMR interpretation could be checked directly by simulating the Al-27 spectrum for a canted versus a collinear spin arrangement; if a non-canted arrangement also yields a double-peak, the assignment would need revision.
The paper leaves open the microscopic exchange mechanism; a natural next step is a model of RKKY interactions on the frustrated triangular rare-earth lattice with an applied field, to see whether the observed growth of the high-field phase with atomic number emerges naturally.

Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

The short version: this paper gives the first NMR and AC susceptibility study of i-MAX magnets, and it finds a high-field phase in Dy, Ho, Er whose ordering temperature rises with field, plus a clean systematic trend with rare-earth atomic number. That part looks real. The interpretive label, 'canted antiferromagnet,' is softer than the abstract suggests; it rests on a double-peak Al-27 NMR line shape that is not simulated or checked against alternative powder line shapes, and the paper itself concedes the AC anomalies might not all be transitions.

What's genuinely new: previous single-crystal work saw high-field anomalies at 2 K but couldn't pin down their nature. This paper extends them to 10-50 K and maps phase boundaries in H-T space. The impurity analysis (XRD re-measurement, listing GdAl2 and Mo3Al2C) is a real improvement over earlier powder studies. The comparison with Barbier et al.'s single-crystal data for the low-field phases is reassuring and suggests the powder data are not random.

Soft spots, in order of severity. First, the canted-AFM claim: the double-peak line shape is interpreted by analogy to [19], but no simulation of Al-27 powder NMR with quadrupolar splitting, anisotropic shift, or a simple collinear state is given. Multi-peak patterns are common in field-swept powder NMR, so this is a real gap. The paper's own discussion says 'we hypothesize' a large FM component, which is closer to the neutron data showing a full FM state along a for Ho at H>2T. If the high-field phase is simply field-polarized FM, the 'unprecedented canted AFM' framing is overreach. Second, the AC-susceptibility assumption: the paper says outright 'we assume that all anomalies measured by AC susceptibility are due to magnetic phase transitions.' That is an explicit assumption, and CEF effects or impurities are not fully excluded for the broad anomalies. The field dependence they cite is suggestive, but not proof. Third, no error bars on the phase diagram markers, despite the claim that marker size covers them. Minor. Fourth, no raw data or analysis code uploaded, which is common but limits reanalysis.

Overall: the dataset is solid and the high-field phase is probably real. The interpretation needs neutron diffraction at high field and at least a basic NMR line-shape simulation. The paper is a good candidate for peer review, but it should be sent back for a strengthened interpretation. I would not cite the canted-AFM conclusion in the next 12 months; I would cite the phase diagram and the impurity-aware measurements.

Referee Report

4 major / 5 minor

Summary. The paper reports AC susceptibility and field-swept Al-27 NMR measurements on powder samples of (Mo2/3RE1/3)2AlC with RE = Gd, Dy, Ho, and Er, and constructs magnetic field-temperature phase diagrams for each compound. The central claim is the discovery of a high-field magnetic phase in Dy-, Ho-, and Er-containing i-MAX compounds, which the authors interpret as a canted antiferromagnetic (AFM) order with a significant ferromagnetic component. The phase is characterized by an anomalously increasing transition temperature with applied field, and the authors argue that this high-field phase grows in field-temperature space as the rare-earth atomic number increases, eventually dominating in Er-i. The manuscript explicitly acknowledges that high-field neutron diffraction would be needed to precisely characterize the magnetic structure.

Significance. If the central claim holds, the paper establishes a previously unreported high-field phase in a family of magnetic i-MAX compounds and provides a systematic comparison across three rare-earth members, which is valuable for the magnetism of nanolaminated materials. The strength of the work is that it combines bulk AC susceptibility with a local probe (Al-27 NMR), reports impurity characterization, and compares powder results with published single-crystal neutron and magnetization data. The main limitation is that the identification of the high-field phase as a canted AFM rests on a qualitative NMR line-shape interpretation without spectral simulation or an independent structural probe, so the central spin-structure claim is not fully established by the evidence presented.

major comments (4)

[Discussion, Fig. 3] The phase diagram is constructed entirely from maxima of the real AC susceptibility chi'(T), and the manuscript states: 'Here we assume that all anomalies measured by AC susceptibility are due to magnetic phase transitions.' This assumption is load-bearing because the central claim of a new ordered high-field phase relies on these anomalies being true thermodynamic transitions. The high-field anomalies are broad, and no frequency-dependent susceptibility data, specific heat, or other thermodynamic probe is shown to distinguish a phase transition from a crossover, a crystalline-electric-field effect, or an impurity response. The observation that the anomalies move to higher temperature with field is suggestive but not sufficient. I recommend either providing additional thermodynamic evidence for at least one representative compound or explicitly softening the claim from 'phase transition' to 'anomaly whose origin requires further study.'
[NMR results (Fig. 2) and Discussion] The assignment of the high-field phase to canted AFM order rests on the Al-27 NMR double-peak line shape being attributed to a canted AFM state, following Ref. [19]. However, for a powder sample of Al-27 (I = 5/2) in a field-swept experiment, multiple peaks can arise from quadrupolar splitting, anisotropic Knight shift, and powder averaging even in a collinear spin structure. The manuscript does not provide a spectral simulation, an estimate of the quadrupolar coupling, or a comparison with alternative spin structures that could produce a similar line shape. Without this, the NMR line shape alone does not uniquely establish canted AFM order. I recommend either adding a simulation or reframing the conclusion as 'consistent with a canted AFM state' rather than a definitive determination.
[Discussion, Ho-i neutron comparison] The manuscript cites neutron diffraction results from Ref. [11] showing that in Ho-i a ferromagnetic component emerges by 1 T and a full FM state along the a-axis is suggested for H > 2 T, while the high-field phase reported here appears only near 4 T. This creates a tension: if the material is already essentially fully polarized along the a-axis above 2 T, the phase observed above 4 T may be better described as a field-polarized or canted FM state rather than a canted AFM. The manuscript should address this discrepancy explicitly and explain why the NMR double-peak structure rules out a simple field-polarized FM interpretation.
[Abstract and Fig. 3] The abstract states that 'as the atomic number of Rare Earth increases, the transition field of this canted AFM phase grows,' but the data in Fig. 3 indicate the opposite for the onset field: the high-field phase in Dy-i appears near 6 T, in Ho-i near 4 T, and in Er-i near 2 T. What grows with atomic number is the extent of the high-field phase in temperature-field space, not the transition field. This wording should be corrected to match the presented phase diagrams.

minor comments (5)

[Title] The title contains a typo: 'Hidden magnetic phases ini -MAX compounds' should read 'Hidden magnetic phases in i-MAX compounds.'
[Results section heading] The heading 'RESUL TS' should be corrected to 'RESULTS.'
[Methods, sample characterization] Table S1 listing significant impurities is mentioned but not shown; please ensure that the supplementary table is included and referenced completely.
[Fig. 2 caption] The notation '0H' is used in the caption and labels but is not defined; it appears to denote the applied field range and should be defined explicitly.
[Er-i transition temperature] The text reports an Er-i zero-field transition at 5.5 K and notes that the literature value is 3.6 K; the discrepancy should be discussed briefly, especially since the powder nature of the sample may affect the measured transition temperature.

Circularity Check

0 steps flagged · score 1.0 of 10

No material circularity: the high-field phase is documented by new NMR and AC-susceptibility data; the canted-AFM label is an interpretation backed by an external neutron study and a previously published NMR fingerprint, not a fitted prediction.

full rationale

The central claim — a high-field phase with growing transition temperature in Dy-i, Ho-i, and Er-i — is constructed directly from measured AC-susceptibility peak positions and field-swept 27Al NMR spectra (Figs. 1–3), with no parameter fitted to the quantity that is then reported as a result. The phase diagram is a direct compilation of χ′(T) maxima: as the paper states, 'Here we assume that all anomalies measured by AC susceptibility are due to magnetic phase transitions.' That is an explicit interpretive assumption, not a fitted input disguised as a prediction. The only step that could raise circularity concerns is the assignment of the NMR double-peak line shape to canted AFM order, supported by reference [19]. Although that reference shares authors with the present work, it is a published, independent experimental study of a different material system and therefore counts as external evidence rather than a restatement of this paper's own result. The paper also cites independent single-crystal neutron diffraction data [11] and explicitly calls for high-field neutron diffraction to confirm the spin structure, so the canted-AFM conclusion is presented as an interpretation to be tested, not as a derivation from the inputs. No equation, fitted parameter, or self-citation chain makes the output equivalent to the input.

Assumptions & free parameters 0 free parameters · 3 assumptions · 0 invented entities

No free parameters were fitted to data; the phase diagram is read off susceptibility maxima. The key assumptions are interpretive, not numerical.

assumptions (3)

domain assumption All anomalies measured by AC susceptibility are magnetic phase transitions.
Explicitly stated in the Discussion. If broad anomalies are crystal-field effects or impurity responses, the high-field phase boundaries would need revision.
domain assumption A double-peak negatively shifted Al-27 NMR line shape is a fingerprint of canted AFM order.
Used to identify the high-field phase as a canted AFM, citing [19]. No simulation or alternative fitting is shown.
domain assumption Most impurity phases have transition temperatures below 10 K and do not affect the measurements, except GdAl2 and Mo3Al2C.
Stated in Methods. Since impurities are present in all samples, the assumption is load-bearing for the low-temperature low-field part of the phase diagram.

how reviews work

0 comments

Cite this review

Pith. "Pith review of Hidden magnetic phases in i-MAX compounds." pith.science (2026). https://pith.science/paper/2SUCMGSZ

@misc{pith2026241202418,
  author       = {Pith},
  title        = {Pith review of: Hidden magnetic phases in i-MAX compounds},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/2SUCMGSZ}},
  note         = {Machine review of arXiv:2412.02418}
}

read the original abstract

We uncover a high-field magnetic phase in i-MAX compounds exhibiting a canted antiferromagnetic (AFM) order with unprecedented properties, revealed through NMR and AC susceptibility. Intriguingly, as the atomic number of Rare Earth increases, the transition field of this canted AFM phase grows at the expense of the lower-field AFM state. Our findings point to the complexity of the magnetic structure in i-MAX compounds, demonstrating a non-trivial evolution of their phase diagram while increasing both the atomic number of the Rare Earth element and the external field.

Figures

Figures reproduced from arXiv: 2412.02418 by the authors.

**Figure 2.** FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗

**Figure 3.** FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗

Figures from the paper (1 more)

**Figure 4.** Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p007_4.png]

Discussion (0). Continue with ORCID to comment.

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Field-induced spin dynamics in i-MAX Tb compound
cond-mat.str-el 2025-01 conditional novelty 5.0 of 10

AC susceptibility of Tb-i-MAX shows frequency-dependent spin dynamics and a probable superparamagnetic state between 0.2 T and 6 T.

Reference graph

Works this paper leans on

19 extracted references · 19 canonical work pages · cited by 1 Pith paper

[19]

Maniv, R

E. Maniv, R. A. Murphy, S. C. Haley, S. Doyle, C. John, A. Maniv, S. K. Ramakrishna, Y.-L. Tang, P. Ercius, R. Ramesh, et al., Nature Physics 17, 525 (2021)

work page 2021
[11]

Barbier, F

M. Barbier, F. Wilhelm, C. V. Colin, C. Opag- iste, E. Lhotel, D. Pinek, Y. Kim, D. Braithwaite, E. Ressouche, P. Ohresser, et al., Physical Review B 105, 174421 (2022)

work page 2022
[1]

M. W. Barsoum, Progress in Solid State Chemistry 28, 201 (2000)

work page 2000
[2]

Dahlqvist, M

M. Dahlqvist, M. W. Barsoum, and J. Rosen, Materials Today (2023)

work page 2023
[3]

Naguib, M

M. Naguib, M. W. Barsoum, and Y. Gogotsi, Advanced Materials 33, 2103393 (2021)

work page 2021
[4]

Dahlqvist, J

M. Dahlqvist, J. Lu, R. Meshkian, Q. Tao, L. Hultman, and J. Ros´ en, Science Advances3, e1700642 (2017)

work page 2017
[5]

Q. Tao, M. Dahlqvist, J. Lu, S. Kota, R. Meshkian, J. Halim, J. Palisaitis, L. Hultman, M. W. Barsoum, P. O. Persson, et al., Nature communications 8, 14949 (2017)

work page 2017
[6]

Q. Tao, J. Lu, M. Dahlqvist, A. Mockute, S. Calder, A. Petruhins, R. Meshkian, O. Rivin, D. Potashnikov, E. N. Caspi, et al., Chemistry of Materials 31, 2476 (2019)

work page 2019

Show all 19 references

[7]

e. a. Yang, J., Carbon 179, 104 (2021)

2021
[8]

e. a. Yang, J., Carbon 183, 76 (2021)

2021
[9]

S. e. a. Sun, Acta Materialia 242, 118479 (2023)

2023
[10]

Z. e. a. Chen, Scripta Materialia 213, 114596 (2022)

2022
[12]

Q. Tao, M. Barbier, A. Mockute, C. Ritter, R. Salikhov, U. Wiedwald, S. Calder, C. Opagiste, R.-M. Galera, M. Farle, et al., Journal of Physics: Condensed Matter 34, 215801 (2022)

2022
[13]

Potashnikov, E

D. Potashnikov, E. Caspi, A. Pesach, Q. Tao, J. Ros´ en, D. Sheptyakov, H. Evans, C. Ritter, Z. Salman, P. Bonfa, et al., Physical Review B 104, 174440 (2021)

2021
[14]

D. S. Williams, P. M. Shand, T. M. Pekarek, R. Skomski, V. Petkov, and D. L. Leslie-Pelecky, Phys. Rev. B 68, 214404 (2003)

2003
[15]

Karki, Y

A. Karki, Y. Xiong, I. Vekhter, D. Browne, P. Adams, D. Young, K. Thomas, J. Y. Chan, H. Kim, and R. Pro- zorov, Physical Review B 82, 064512 (2010)

2010
[16]

H. S. Lee, H. B. Kim, R. E. Kim, W. C. Ri, B. K. Cho, and J. J. Oh, Journal of the Korean Physical Society 34, 88 (1999)

1999
[17]

Yahav, D

D. Yahav, D. Potashnikov, A. Pesach, O. Rivin, E. N. Caspi, J. Rosen, M. Schechter, A. Maniv, and E. Maniv, (Preprint) (2024)

2024
[18]

S. C. Haley, S. F. Weber, T. Cookmeyer, D. E. Parker, E. Maniv, N. Maksimovic, C. John, S. Doyle, A. Maniv, S. K. Ramakrishna, et al., Physical Review Research 2, 043020 (2020)

2020

Pith tools

Reviewed August 11, 2026 · model on record in the stance chip above.

[1] [19]

Maniv, R

E. Maniv, R. A. Murphy, S. C. Haley, S. Doyle, C. John, A. Maniv, S. K. Ramakrishna, Y.-L. Tang, P. Ercius, R. Ramesh, et al., Nature Physics 17, 525 (2021)

work page 2021

[2] [11]

Barbier, F

M. Barbier, F. Wilhelm, C. V. Colin, C. Opag- iste, E. Lhotel, D. Pinek, Y. Kim, D. Braithwaite, E. Ressouche, P. Ohresser, et al., Physical Review B 105, 174421 (2022)

work page 2022

[3] [1]

M. W. Barsoum, Progress in Solid State Chemistry 28, 201 (2000)

work page 2000

[4] [2]

Dahlqvist, M

M. Dahlqvist, M. W. Barsoum, and J. Rosen, Materials Today (2023)

work page 2023

[5] [3]

Naguib, M

M. Naguib, M. W. Barsoum, and Y. Gogotsi, Advanced Materials 33, 2103393 (2021)

work page 2021

[6] [4]

Dahlqvist, J

M. Dahlqvist, J. Lu, R. Meshkian, Q. Tao, L. Hultman, and J. Ros´ en, Science Advances3, e1700642 (2017)

work page 2017

[7] [5]

Q. Tao, M. Dahlqvist, J. Lu, S. Kota, R. Meshkian, J. Halim, J. Palisaitis, L. Hultman, M. W. Barsoum, P. O. Persson, et al., Nature communications 8, 14949 (2017)

work page 2017

[8] [6]

Q. Tao, J. Lu, M. Dahlqvist, A. Mockute, S. Calder, A. Petruhins, R. Meshkian, O. Rivin, D. Potashnikov, E. N. Caspi, et al., Chemistry of Materials 31, 2476 (2019)

work page 2019