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arxiv: 2604.02898 · v1 · submitted 2026-04-03 · ❄️ cond-mat.str-el · cond-mat.mtrl-sci

Microscopic NMR evidence for successive antiferroelectric and antiferromagnetic order in the van der Waals magnet CuCrP₂S₆

Pith reviewed 2026-05-13 17:55 UTC · model grok-4.3

classification ❄️ cond-mat.str-el cond-mat.mtrl-sci
keywords NMRvan der Waals magnetantiferroelectric orderantiferromagnetic ordercritical exponentCuCrP2S6phase transitionsphosphorus sites
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The pith

NMR line splitting reveals two inequivalent phosphorus sites in the antiferroelectric phase of CuCrP2S6, with relaxation data placing the magnetic order in the three-dimensional Heisenberg class.

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

The study tracks the temperature evolution of 31P and 65Cu NMR spectra, shifts, and relaxation rates through the sequence of transitions in this layered van der Waals compound. Below the antiferroelectric transition near 150 K the NMR line splits and the spin-lattice relaxation rate shows distinct behavior for the two resulting phosphorus environments. Near the antiferromagnetic ordering temperature of 30 K the relaxation rate diverges with a critical exponent of approximately 0.45, consistent with three-dimensional Heisenberg universality. From the shift data the authors extract nearly isotropic hyperfine couplings and a dominant dipolar contribution to the anisotropy, together with an intralayer ferromagnetic exchange of about -4.9 K.

Core claim

Microscopic 31P NMR establishes that the long-range antiferroelectric order below 150 K produces two inequivalent phosphorus sites whose distinct environments are directly visible in both the resonance line and the relaxation rate; the same measurements show that the antiferromagnetic transition at 30 K belongs to the three-dimensional Heisenberg universality class with critical exponent γ ≃ 0.45.

What carries the argument

Splitting of the 31P NMR line together with the critical divergence of the spin-lattice relaxation rate T1^{-1} near TN, which together fingerprint the two phosphorus environments created by antiferroelectric order and the magnetic universality class.

If this is right

  • Intralayer exchange is ferromagnetic with J_intra ≈ -4.9 K while interlayer coupling is antiferromagnetic, producing the observed ordering.
  • Transferred hyperfine couplings at the phosphorus sites are nearly isotropic.
  • The observed NMR shift anisotropy is dominated by the dipolar field rather than by transferred hyperfine anisotropy.
  • The Moriya high-temperature relaxation rate, including P-P dimer cross-correlation effects, accounts for the measured T1^{-1} above the ordering temperature.

Where Pith is reading between the lines

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

  • The same NMR signatures of site inequivalence could be used to detect antiferroelectric order in isostructural van der Waals compounds where diffraction resolution is limited.
  • The 3D Heisenberg exponent implies that weak interlayer couplings are sufficient to stabilize three-dimensional critical behavior despite the layered crystal structure.
  • Because the hyperfine field is largely dipolar, the NMR shift can serve as a direct local probe of the ordered moment direction once the antiferromagnetic structure is known.

Load-bearing premise

The NMR line splitting and relaxation changes arise exclusively from the antiferroelectric order creating two distinct phosphorus environments, without significant contributions from other structural distortions or impurity phases.

What would settle it

An independent structural probe that finds no additional phosphorus-site distinction or lattice distortion exactly at the 150 K transition, or an NMR spectrum that remains unsplit below that temperature, would contradict the claim that the splitting directly signals antiferroelectric order.

Figures

Figures reproduced from arXiv: 2604.02898 by B. B\"uchner, C. S. Saramgi, H.-J. Grafe, K. M. Ranjith, L. F. Prager, S. Aswartham, S. Selter, Y. Shemerliuk.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7 [PITH_FULL_IMAGE:figures/full_fig_p007_7.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9 [PITH_FULL_IMAGE:figures/full_fig_p008_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: At high temperatures, the echo envelope exhibits pronounced oscillations, reflecting the dipolar coupling within the P–P dimer of the [P2S6] 4− unit. The decay is well described by the standard Gaussian-modulated oscillatory form M(τ ) = M0 exp[ − 1 2 ( 2τ T2G )2 ] × [ 1 − F e−2τ/T2 cos(2ωτ − ψ) ] , (6) where T2G captures the static second moment of the local dipolar field distribution, ω is the P–P dipol… view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11 [PITH_FULL_IMAGE:figures/full_fig_p010_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: FIG. 12 [PITH_FULL_IMAGE:figures/full_fig_p011_12.png] view at source ↗
read the original abstract

We present a comprehensive $^{31}$P and $^{65}$Cu nuclear magnetic resonance (NMR) study of the layered van der Waals magnet CuCrP$_2$S$_6$. The compound exhibits a sequence of structural and magnetic phase transitions: a high-temperature paraelectric state, followed by a quasi-antiferroelectric (QAFE) state near 185 K, a long-range antiferroelectric (AFE) phase below 150 K, and finally, antiferromagnetic (AFM) order below $T_\mathrm{N}$ = 30 K. The evolution of the NMR spectra, NMR shift, and spin-lattice ($T_1^{-1}$) and spin-spin ($T_2^{-1}$) relaxation rates provide direct microscopic fingerprints of these transitions. The splitting of both the NMR line and $T_1^{-1}$ below the AFE transition demonstrates the emergence of two inequivalent P sites. From $K - \chi$ analysis, we extract nearly isotropic transferred hyperfine couplings and show that the NMR shift anisotropy originates primarily from the dipolar contribution, in contrast to Mn$_2$P$_2$S$_6$ and Ni$_2$P$_2$S$_6$. We determine the ferromagnetic intralayer exchange $J_{intra}\approx$ -4.9 K from the Curie Weiss temperature, consistent with ferromagnetic layers antiferromagnetically stacked along the $c$ axis, and evaluate the Moriya high temperature relaxation rate including cross correlation effects of the P P dimer. Critical divergence of $T_1^{-1}$ near $T_\mathrm{N}$ yields a critical exponent $\gamma\simeq$ 0.45(4), placing CuCrP$_2$S$_6$ in a three dimensional Heisenberg universality regime.

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

1 major / 2 minor

Summary. The manuscript reports a comprehensive 31P and 65Cu NMR study of the layered van der Waals magnet CuCrP2S6. It identifies a sequence of transitions from a high-temperature paraelectric state to a quasi-antiferroelectric (QAFE) state near 185 K, long-range antiferroelectric (AFE) order below 150 K, and antiferromagnetic (AFM) order below TN = 30 K. The evolution of NMR spectra, shifts (K), and relaxation rates (T1^{-1}, T2^{-1}) is presented as direct microscopic evidence for these phases. Key results include splitting of the NMR line and T1^{-1} into two components below the AFE transition (indicating inequivalent P sites), extraction of nearly isotropic transferred hyperfine couplings via K-χ analysis, determination of ferromagnetic intralayer exchange J_intra ≈ -4.9 K from the Curie-Weiss temperature, and a critical exponent γ ≃ 0.45(4) from the divergence of T1^{-1} near TN, consistent with 3D Heisenberg universality. The work contrasts the anisotropy origin with related compounds Mn2P2S6 and Ni2P2S6 and includes Moriya high-temperature relaxation analysis accounting for P-P dimer cross correlations.

Significance. If the interpretations hold, the study supplies useful microscopic NMR fingerprints for the successive structural and magnetic orders in this van der Waals system, including a critical exponent that supports assignment to the 3D Heisenberg class. The K-χ analysis and relaxation-rate modeling with cross-correlation effects represent solid technical contributions that allow direct comparison to other MPS3-family materials. These elements strengthen the case for NMR as a probe of coupled ferroelectric and magnetic degrees of freedom in layered magnets.

major comments (1)
  1. [Abstract and AFE-transition results section] Abstract and the section describing the AFE transition (NMR line splitting and T1^{-1} below 150 K): the central claim that the observed splitting demonstrates two inequivalent P sites created exclusively by long-range antiferroelectric order is load-bearing for the microscopic-evidence narrative, yet the manuscript does not explicitly address or rule out contributions from minor lattice distortions, stacking faults, or undetected impurity phases. Additional spectra, intensity analysis, or temperature-hysteresis checks would be required to secure this interpretation.
minor comments (2)
  1. [Critical divergence analysis near TN] The reported critical exponent γ ≃ 0.45(4) lacks details on the fitting procedure, temperature window, and uncertainty estimation; including these would allow readers to assess the robustness of the 3D Heisenberg assignment.
  2. [Introduction and phase-transition overview] Notation for the intermediate phase is introduced as both 'quasi-antiferroelectric (QAFE)' and 'quasi-antiferroelectric state' without a clear definition of the distinction from the long-range AFE phase; a brief clarifying sentence would improve readability.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful and constructive review of our manuscript. We respond to the single major comment below and indicate the revisions we will make.

read point-by-point responses
  1. Referee: [Abstract and AFE-transition results section] Abstract and the section describing the AFE transition (NMR line splitting and T1^{-1} below 150 K): the central claim that the observed splitting demonstrates two inequivalent P sites created exclusively by long-range antiferroelectric order is load-bearing for the microscopic-evidence narrative, yet the manuscript does not explicitly address or rule out contributions from minor lattice distortions, stacking faults, or undetected impurity phases. Additional spectra, intensity analysis, or temperature-hysteresis checks would be required to secure this interpretation.

    Authors: We agree that an explicit discussion of alternative origins would strengthen the presentation. The splitting of the 31P line into two components of equal integrated intensity occurs sharply at 150 K, matching the long-range AFE transition temperature established by prior dielectric and X-ray studies on the same compound. The simultaneous splitting of T1^{-1} into two distinct values below this temperature further supports an intrinsic structural origin tied to the AFE order. Minor lattice distortions or stacking faults in van der Waals layers typically produce inhomogeneous broadening or a continuous shift distribution rather than two well-resolved, equal-intensity lines. Undetected impurity phases would not exhibit the same temperature onset or the correlated splitting in both the spectrum and relaxation rate, nor would they align with the magnetic critical behavior near TN. Intensity analysis showing equal areas for the two lines is already contained in the figures. To address the referee's concern directly, we will add a concise paragraph in the revised AFE-transition section (and update the abstract if needed) that explicitly considers these alternatives and explains why the data favor two inequivalent P sites due to long-range AFE order. Because the present dataset does not include new temperature-hysteresis or additional spectra, we cannot supply those; we will note this limitation and the value of such checks for future work. This is therefore a partial revision. revision: partial

Circularity Check

0 steps flagged

No significant circularity in derivation chain

full rationale

The paper extracts J_intra from the Curie-Weiss temperature via standard mean-field fitting and obtains the critical exponent γ by fitting the divergence of T1^{-1} near TN; both are conventional data reductions from independent experimental inputs rather than self-referential derivations. The central claim of two inequivalent P sites rests on direct observation of NMR line splitting and T1^{-1} changes below the AFE transition, without any equation reducing the output to the input by construction. No self-citations, uniqueness theorems, or ansatzes imported from prior work by the same authors appear as load-bearing steps. The derivation chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

2 free parameters · 2 axioms · 0 invented entities

The central claims rest on standard NMR shift and relaxation interpretations plus two fitted parameters extracted from susceptibility and relaxation data.

free parameters (2)
  • J_intra = -4.9 K
    Ferromagnetic intralayer exchange extracted from the Curie-Weiss temperature.
  • gamma = 0.45(4)
    Critical exponent obtained by fitting the divergence of T1^{-1} near TN.
axioms (2)
  • domain assumption NMR line splitting below the AFE transition arises solely from two inequivalent phosphorus sites created by the antiferroelectric order.
    Invoked to interpret the observed spectral splitting as direct evidence of the AFE phase.
  • domain assumption The high-temperature relaxation rate follows the Moriya expression including cross-correlation effects of the P-P dimer.
    Used to evaluate the relaxation data above TN.

pith-pipeline@v0.9.0 · 5683 in / 1501 out tokens · 93673 ms · 2026-05-13T17:55:36.967397+00:00 · methodology

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Reference graph

Works this paper leans on

59 extracted references · 59 canonical work pages

  1. [1]

    Paramagnetic state The 31P nucleus ( I = 1 2 ) provides a clean magnetic probe without quadrupolar complications, making the spectral line shape an excellent indicator of changes in the local structural and magnetic environments. At high temperatures, where CuCrP 2S6 crystallizes in the mono- clinic C2/c structure, all P atoms are crystallographically equ...

  2. [2]

    NMR shift and hyperfine coupling The NMR shift K(T ) provides a direct measure of the local spin susceptibility at the P site and there- fore serves as a sensitive probe of how magnetic corre- lations evolve through the structural transitions. In the high-temperature paraelectric phase, the single crystallo- graphic P site yields a single NMR shift value ...

  3. [3]

    These fields produce additional splittings 7 /s52/s50 /s52/s52 /s52/s54 /s52/s56 /s53/s48 FIG

    Magnetically ordered state At the Néel temperature TN = 30 K, the Cr 3+ sublat- tice in CuCrP 2S6 develops long-range antiferromagnetic order, which generates static internal hyperfine fields at the 31P sites. These fields produce additional splittings 7 /s52/s50 /s52/s52 /s52/s54 /s52/s56 /s53/s48 FIG. 7. 31P NMR spectra in the antiferromagnetic state me...

  4. [4]

    Spin-lattice relaxation rate T −1 1 Figure 9(a) and (b) show temperature dependence of the spin-lattice relaxation rate T −1 1 (T ) measured at dif- ferent magnetic fields applied along b and c∗ axes, re- spectively. At high temperatures ( T ≳ 180 K), T −1 1 (T ) is nearly temperature independent, consistent with the exchange-narrowed limit expected for r...

  5. [5]

    Representative spin–echo de- cays obtained at selected temperatures are shown in Fig

    Spin-spin relaxation rate T −1 2 The transverse spin–spin relaxation rate T −1 2 of 31P provides additional insight into the evolution of local magnetic and electric fluctuations across the structural and magnetic transitions. Representative spin–echo de- cays obtained at selected temperatures are shown in Fig. 10. At high temperatures, the echo envelope ...

  6. [6]

    K. S. Novoselov, A. Mishchenko, A. Carvalho, and A. Castro Neto, 2D materials and van der Waals het- erostructures, Science 353, aac9439 (2016)

  7. [7]

    A. K. Geim and I. V. Grigorieva, Van der Waals het- erostructures, Nature 499, 419 (2013)

  8. [8]

    Huang, G

    B. Huang, G. Clark, E. Navarro-Moratalla, D. R. Klein, R. Cheng, K. L. Seyler, D. Zhong, E. Schmidgall, M. A. McGuire, D. H. Cobden, et al. , Layer-dependent ferro- magnetism in a van der Waals crystal down to the mono- layer limit, Nature 546, 270 (2017)

  9. [9]

    Gibertini, M

    M. Gibertini, M. Koperski, A. F. Morpurgo, and K. S. Novoselov, Magnetic 2D materials and heterostructures, Nature nanotechnology 14, 408 (2019)

  10. [10]

    Gong and X

    C. Gong and X. Zhang, Two-dimensional magnetic crys- tals and emergent heterostructure devices, Science 363, eaav4450 (2019)

  11. [11]

    K. S. Burch, D. Mandrus, and J.-G. Park, Magnetism in two-dimensional van der Waals materials, Nature 563, 47 (2018)

  12. [12]

    H. Xu, S. Xu, X. Xu, J. Zhuang, W. Hao, and Y. Du, Re- cent advances in two-dimensional van der waals magnets, Microstructures 2, 2022011 (2022)

  13. [13]

    Bonilla, S

    M. Bonilla, S. Kolekar, Y. Ma, H. C. Diaz, V. Kalappattil, R. Das, T. Eggers, H. R. Gutierrez, M.-H. Phan, and M. Batzill, Strong room-temperature ferromagnetism in VSe2 monolayers on van der Waals substrates, Nature nanotechnology 13, 289 (2018)

  14. [14]

    Z. Zhao, L. Ma, M. Men, W. Li, and X. Wang, All two- dimensional van der Waals magnetic tunneling junctions, Applied Physics Reviews 12 (2025)

  15. [15]

    Zhang, P

    B. Zhang, P. Lu, R. Tabrizian, P. X.-L. Feng, and Y. Wu, 2D magnetic heterostructures: spintronics and quantum future, npj Spintronics 2, 6 (2024)

  16. [16]

    Brec, Review on structural and chemical properties of transition metal phosphorous trisulfides MPS 3, Solid State Ionics 22, 3 (1986)

    R. Brec, Review on structural and chemical properties of transition metal phosphorous trisulfides MPS 3, Solid State Ionics 22, 3 (1986)

  17. [17]

    Van Koughnet, B

    K. Van Koughnet, B. Mallett, S. Chong, B. S. Conner, M. A. McGuire, M. A. Susner, and R. G. Buckley, Spin- lattice and spin-electronic interactions in the van der Waals semiconductor Co 2P2S6, Physical Review B 109, 165142 (2024)

  18. [18]

    C. C. Mayorga-Martinez, Z. Sofer, D. Sedmidubsky, S. Huber, A. Y. S. Eng, and M. Pumera, Layered metal thiophosphite materials: magnetic, electrochemical, and electronic properties, ACS applied materials & interfaces 9, 12563 (2017)

  19. [19]

    Cheng, Y.-S

    M. Cheng, Y.-S. Lee, A. K. Iyer, D. G. Chica, E. K. Qian, M. A. Shehzad, R. Dos Reis, M. G. Kanatzidis, and V. P. 13 Dravid, Mixed metal thiophosphate Fe 2−xCoxP2S6: role of structural evolution and anisotropy, Inorganic chem- istry 60, 17268 (2021)

  20. [20]

    Synnatschke, S

    K. Synnatschke, S. Shao, J. Van Dinter, Y. J. Hofstetter, D. J. Kelly, S. Grieger, S. J. Haigh, Y. Vaynzof, W. Ben- sch, and C. Backes, Liquid exfoliation of Ni 2P2S6: struc- tural characterization, size-dependent properties, and degradation, Chemistry of Materials 31, 9127 (2019)

  21. [21]

    Shemerliuk, Y

    Y. Shemerliuk, Y. Zhou, Z. Yang, G. Cao, A. U. Wolter, B. Büchner, and S. Aswartham, Tuning magnetic and transport properties in quasi-2D (Mn 1−xNix)2P2S6 sin- gle crystals, Electronic Materials 2, 284 (2021)

  22. [22]

    Senyk, J

    Y. Senyk, J. J. Abraham, Y. Shemerliuk, S. Selter, S. Aswartham, B. Büchner, V. Kataev, and A. Alfonsov, Evolution of the spin dynamics in the van der Waals sys- tem M2P2S6 (M2 = Mn 2, MnNi, Ni2) series probed by electron spin resonance spectroscopy, Phys. Rev. Mater. 7, 014003 (2023)

  23. [23]

    J. J. Abraham, Y. Senyk, Y. Shemerliuk, S. Selter, S. Aswartham, B. Büchner, V. Kataev, and A. Alfonsov, Magnetic anisotropy and low-energy spin dynamics in the van der Waals compounds Mn2P2S6 and MnNiP2S6, Phys. Rev. B 107, 165141 (2023)

  24. [24]

    A. R. Wildes, V. Simonet, E. Ressouche, G. J. McIn- tyre, M. A vdeev, E. Suard, S. A. J. Kimber, D. Lançon, G. Pepe, B. Moubaraki, and T. J. Hicks, Magnetic struc- ture of the quasi-two-dimensional antiferromagnet NiPS 3, Phys. Rev. B 92, 224408 (2015)

  25. [25]

    A. P. Dioguardi, S. Selter, U. Peeck, S. Aswartham, M.-I. Sturza, R. Murugesan, M. S. Eldeeb, L. Hozoi, B. Büch- ner, and H.-J. Grafe, Quasi-two-dimensional magnetic correlations in Ni2P2S6 probed by 31P NMR, Phys. Rev. B 102, 064429 (2020)

  26. [26]

    Bougamha, S

    F. Bougamha, S. Selter, Y. Shemerliuk, S. Aswartham, A. Benali, B. Büchner, H.-J. Grafe, and A. P. Dioguardi, 31P NMR investigation of quasi-two-dimensional mag- netic correlations in T2P2S6 (T = Mn, Ni), Phys. Rev. B 105, 024410 (2022)

  27. [27]

    Upreti, R

    D. Upreti, R. Basnet, M. Sharma, S. K. Chhetri, G. Acharya, M. R. U. Nabi, J. Sakon, M. Bena- mara, M. Mortazavi, and J. Hu, Medium-entropy engineering of magnetism in layered antiferromagnet CuxNi2(1−x)CrxP2S6, Advanced Functional Materials 35, 2418722 (2025)

  28. [28]

    Selter, K

    S. Selter, K. K. Bestha, P. Bhattacharyya, B. Özer, Y. Shemerliuk, M. Roslova, E. Vinokurova, L. Corre- dor, L. Veyrat, A. Wolter, et al. , Crystal growth, ex- foliation, and magnetic properties of quaternary quasi- two-dimensional CuCrP 2S6, Physical Review Materials 7, 033402 (2023)

  29. [29]

    P. Luo, S. Qu, Z. Zhou, W. Li, L. Gao, H. Jiang, X. Liu, and Y. Zheng, Magnetism and magnetoelectric coupling in the van der Waals antiferromagnet CuCr 1−xVxP2S6, Physical Review B 111, 224408 (2025)

  30. [30]

    M. Hong, L. Dai, H. Hu, and C. Li, Structural, ferroelec- tric, and electronic transitions in the van der Waals mul- tiferroic material CuCrP 2S6 under high temperature and high pressure, Physical Review B 110, 144103 (2024)

  31. [31]

    M. A. Susner, R. Rao, A. T. Pelton, M. V. McLeod, and B. Maruyama, Temperature-dependent Raman scatter- ing and x-ray diffraction study of phase transitions in lay- ered multiferroic CuCrP2S6, Phys. Rev. Mater. 4, 104003 (2020)

  32. [32]

    Maisonneuve, V

    V. Maisonneuve, V. Cajipe, and C. Payen, Low- temperature neutron powder diffraction study of copper chromium thiophosphate (CuCrP 2S6): observation of an ordered, antipolar copper sublattice, Chemistry of Mate- rials 5, 758 (1993)

  33. [33]

    Maisonneuve, C

    V. Maisonneuve, C. Payen, and V. Cajipe, On CuCrP 2S6: copper disorder, stacking distortions, and magnetic order- ing, Journal of Solid State Chemistry 116, 208 (1995)

  34. [34]

    V. B. Cajipea, J. Ravez, V. Maisonneuve, A. Simon, C. Payen, R. V. D. Muhll, and J. E. Fischer, Copper ordering in lamellar cump2s6 (m= cr, in): Transition to an antiferroelectric or ferroelectric phase, Ferroelectrics 185, 135 (1996)

  35. [35]

    I. P. Studenyak, O. A. Mykajlo, Y. M. Vysochanskii, and V. B. Cajipe, Optical absorption studies of phase tran- sitions in cucrp2s6 layered antiferroelectrics, Journal of Physics: Condensed Matter 15, 6773 (2003)

  36. [36]

    C. B. Park, A. Shahee, K.-T. Kim, D. R. Patil, S. A. Guda, N. Ter-Oganessian, and K. H. Kim, Observation of spin-induced ferroelectricity in a layered van der Waals antiferromagnet CuCrP2S6, Advanced Electronic Materi- als 8, 2101072 (2022)

  37. [37]

    W. F. Io, S.-Y. Pang, L. W. Wong, Y. Zhao, R. Ding, J. Mao, Y. Zhao, F. Guo, S. Yuan, J. Zhao, et al. , Direct observation of intrinsic room-temperature ferroelectric- ity in 2D layered CuCrP 2S6, Nature communications 14, 7304 (2023)

  38. [38]

    J. Tang, B. J. Lawrie, M. Cheng, Y.-C. Wu, H. Zhao, D. Kong, R. Lu, C.-H. Yao, Z. Gai, A.-P. Li, et al. , Raman fingerprints of phase transitions and ferroic cou- plings in van der Waals multiferroic CuCrP 2S6, The Jour- nal of Physical Chemistry Letters 16, 4336 (2025)

  39. [39]

    J. J. Abraham, Y. Guo, Y. Shemerliuk, S. Selter, S. Aswartham, K. K. Bestha, L. T. Corredor, A. U. Wolter, O. Kataeva, L. Rogić, et al. , Magnetic-field tun- ing of the spin dynamics in the quasi-2D van der Waals antiferromagnet CuCrP 2S6, Advanced Functional Mate- rials , e11057 (2025)

  40. [40]

    Abragam, Principles of Nuclear Magnetism (Oxford University Press, Oxford, 1961)

    A. Abragam, Principles of Nuclear Magnetism (Oxford University Press, Oxford, 1961)

  41. [41]

    C. P. Slichter, Principles of Magnetic Resonance , 3rd ed., Springer Series in Solid-State Sciences (Springer, Berlin and Heidelberg, 1990)

  42. [42]

    Narath, Nuclear spin-lattice relaxation in hexagonal transition metals: Titanium, Physical Review 162, 320 (1967)

    A. Narath, Nuclear spin-lattice relaxation in hexagonal transition metals: Titanium, Physical Review 162, 320 (1967)

  43. [43]

    G. E. Pake, Nuclear resonance absorption in hydrated crystals: Fine structure of the proton line, J. Chem. Phys. 16, 327 (1948)

  44. [44]

    Titze, G

    A. Titze, G. Hinze, and R. Böhmer, Antiferroelectric phase transition in Rb3D(SO4)2 single crystals studied by 87Rb NMR, Phys. Rev. B 57, R666 (1998)

  45. [45]

    Moriya, N

    K. Moriya, N. Kariya, A. Inaba, T. Matsuo, I. Pritz, and Y. M. Vysochanskii, Low-temperature calorimetric study of phase transitions in CuCrP 2S6, Solid State Communi- cations 136, 173 (2005)

  46. [46]

    A. M. Clogston and V. Jaccarino, Susceptibilities and negative knight shifts of intermetallic compounds, Phys. Rev. 121, 1357 (1961)

  47. [47]

    Belesi, F

    M. Belesi, F. Borsa, and A. K. Powell, Evidence for spin- wave excitations in the long-range magnetically ordered state of a Fe19 molecular crystal from proton NMR, Phys. Rev. B 74, 184408 (2006) . 14

  48. [48]

    R. Nath, K. M. Ranjith, B. Roy, D. C. Johnston, Y. Fu- rukawa, and A. A. Tsirlin, Magnetic transitions in the spin- 5 2 frustrated magnet BiMn2PO6 and strong lattice softening in BiMn2PO6 and BiZn2PO6 below 200 K, Phys. Rev. B 90, 024431 (2014)

  49. [49]

    Moriya, Nuclear magnetic relaxation in antiferromag- netics, Progress of Theoretical Physics 16, 23 (1956)

    T. Moriya, Nuclear magnetic relaxation in antiferromag- netics, Progress of Theoretical Physics 16, 23 (1956)

  50. [50]

    Freude, Spin-lattice relaxation, lecture notes, available at https://www.dieter-freude.de/quad-nmr/7.pdf

    D. Freude, Spin-lattice relaxation, lecture notes, available at https://www.dieter-freude.de/quad-nmr/7.pdf

  51. [51]

    W.-L. Ma, G. Wolfowicz, N. Zhao, S.-S. Li, J. J. Mor- ton, and R.-B. Liu, Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoher- ence, Nature communications 5, 4822 (2014)

  52. [52]

    Moriya, Nuclear magnetic relaxation near the curie temperature, Progress of Theoretical Physics 28, 371 (1962)

    T. Moriya, Nuclear magnetic relaxation near the curie temperature, Progress of Theoretical Physics 28, 371 (1962)

  53. [53]

    B. I. Halperin and P. C. Hohenberg, Generalization of scaling laws to dynamical properties of a system near its critical point, Phys. Rev. Lett. 19, 700 (1967)

  54. [54]

    Takeya, K

    H. Takeya, K. Ishida, K. Kitagawa, Y. Ihara, K. Onuma, Y. Maeno, Y. Nambu, S. Nakatsuji, D. E. MacLaugh- lin, A. Koda, and R. Kadono, Spin dynamics and spin freezing behavior in the two-dimensional antiferromagnet Niga2s4 revealed by ga-nmr, nqr and µSR measurements, Phys. Rev. B 77, 054429 (2008)

  55. [55]

    L. J. de Jongh, Magnetic properties of layered transition metal compounds (Springer Science & Business Media, 2012)

  56. [56]

    Oyamada, S

    A. Oyamada, S. Maegawa, M. Nishiyama, H. Kitazawa, and Y. Isikawa, Ordering mechanism and spin fluctua- tions in a geometrically frustrated heavy-fermion antifer- romagnet on the kagome-like lattice cepdal: A 27Al nmr study, Phys. Rev. B 77, 064432 (2008)

  57. [57]

    M. F. Collins, Magnetic critical scattering, Vol. 4 (Oxford university press, 1989)

  58. [58]

    Y. Itoh, C. Michioka, K. Yoshimura, K. Nakajima, and H. Sato, Critical slowing down of triangular lattice spin- 3/2 heisenberg antiferromagnet li7ruo6 via 7li nmr, Jour- nal of the Physical Society of Japan 78, 023705 (2009)

  59. [59]

    R. J. Birgeneau, Spin correlations in the two-dimensional s=1 heisenberg antiferromagnet, Phys. Rev. B 41, 2514 (1990)