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arxiv: 2606.06146 · v1 · pith:LBVW5MEYnew · submitted 2026-06-04 · ❄️ cond-mat.mtrl-sci

Stacking-Dependent Magnetism and Tunable Half-Metallicity in Bilayer Janus 1T-MnSSe

Jakkapat Seeyangnok , Udomsilp Pinsook , Graeme J. Ackland This is my paper

Pith reviewed 2026-06-28 00:42 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords bilayer MnSSeJanus materialsstacking-dependent magnetismhalf-metallicitytwo-dimensional magnetsantiferromagnetic orderingspintronics
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0 comments X

The pith

Bilayer Janus MnSSe has stacking-dependent magnetism with transition temperatures above room temperature and half-metallic states tunable by doping or strain.

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

The calculations examine how different ways of aligning the two layers in bilayer 1T-MnSSe affect its magnetic and electronic behavior. The AA2 stacking emerges as the lowest-energy arrangement and shows antiferromagnetic coupling between the layers. An effective model fitted to the computed energies and sampled with Monte Carlo methods yields magnetic ordering temperatures well above 300 K in antiferromagnetic cases and up to 250 K in ferromagnetic ones. Several stackings produce half-metallic ferromagnetism in which one spin channel is fully conducting while the other is gapped, and this polarization can be driven to zero by adding charge carriers or stretching the lattice. These results indicate that the material's magnetic order and spin-dependent transport can be controlled through the choice of layer registry.

Core claim

The AA2 stacking is the ground state and exhibits A-type antiferromagnetic ordering, indicating antiferromagnetic interlayer coupling. Monte Carlo simulations based on an effective Ising model reveal enhanced magnetic transition temperatures in the bilayer relative to the monolayer, with Néel temperatures above 300 K for antiferromagnetic stackings and Curie temperatures up to 250 K for ferromagnetic phases. Several stacking configurations exhibit robust half-metallic ferromagnetism with nearly 100% spin polarization at the Fermi level. The half-metallic state can be tuned and ultimately transformed into a metallic ferromagnetic phase through carrier doping and biaxial strain.

What carries the argument

The AA- and AB-type stacking configurations of the bilayer, which fix the relative positions of the S and Se atoms across the van der Waals gap and thereby set the sign and strength of the interlayer exchange and the spin-polarized band structure.

If this is right

  • Antiferromagnetic stackings remain ordered well above room temperature while ferromagnetic ones order below it.
  • Multiple stackings produce half-metallic ferromagnetism with essentially complete spin polarization at the Fermi level.
  • The half-metallic gap can be closed and the system driven into a conventional metallic ferromagnet by either electron or hole doping or by biaxial strain.
  • The nonmagnetic state is unstable for every stacking examined, so magnetism is intrinsic rather than induced.

Where Pith is reading between the lines

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

  • If specific stackings can be selected during growth or by twisting, the same material could serve as either an antiferromagnetic insulator or a half-metallic conductor without external magnetic fields.
  • The same stacking-to-property mapping may appear in other Janus transition-metal dichalcogenides that combine similar magnetic ions with different chalcogens.
  • Carrier doping and strain act as orthogonal knobs that could allow gate-tunable switching between fully polarized and unpolarized transport in a single device geometry.

Load-bearing premise

The total energies obtained from first-principles calculations can be faithfully represented by a simple Ising model whose parameters, once extracted, allow Monte Carlo sampling to give accurate ordering temperatures without missing longer-range or anisotropic interactions.

What would settle it

Direct measurement of a Néel temperature above 300 K or a Curie temperature near 250 K in an AA2-stacked sample, or spectroscopic confirmation of 100 percent spin polarization at the Fermi level in a ferromagnetic stacking that disappears under moderate doping or strain.

Figures

Figures reproduced from arXiv: 2606.06146 by Graeme J. Ackland, Jakkapat Seeyangnok, Udomsilp Pinsook.

Figure 1
Figure 1. Figure 1: FIG. 1. Top and side views of the considered primitive cell of bilayer stacking configurations. The AA-type stackings are labeled as AA1, [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: For all stackings, the nonmagnetic (NM) state is sig [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. (a) Spin-resolved electronic band structure and projected density of states (PDOS) of the ML-MnSSe monolayer, where blue and red [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Spin-resolved electronic band structures and corresponding projected density of states (PDOS) of van der Waals bilayer Janus MnSSe [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Temperature dependence of the magnetic order parameter for monolayer (ML) and bilayer (BL) MnSSe obtained from Monte Carlo [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. (a) Spin gap as a function of carrier doping for different stacking configurations (AA1, AA3, AB2, and AB3) in bilayer MnSSe. The [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
read the original abstract

We investigate the structural, electronic, and magnetic properties of bilayer Janus 1T-MnSSe using first-principles calculations. Various AA- and AB-type stacking configurations are considered to examine the influence of interlayer registry on magnetic ordering and exchange interactions. The nonmagnetic state is unstable for all stackings, confirming intrinsic magnetism. The AA2 stacking is identified as the ground state and exhibits A-type antiferromagnetic ordering, indicating antiferromagnetic interlayer coupling. Monte Carlo simulations based on an effective Ising model reveal enhanced magnetic transition temperatures in the bilayer relative to the monolayer, with N\'eel temperatures above 300~K for antiferromagnetic stackings and Curie temperatures up to 250~K for ferromagnetic phases. Several stacking configurations exhibit robust half-metallic ferromagnetism with nearly 100\% spin polarization at the Fermi level. Moreover, the half-metallic state can be tuned and ultimately transformed into a metallic ferromagnetic phase through carrier doping and biaxial strain. These findings establish bilayer MnSSe as a promising platform for controllable interlayer magnetism and spintronic applications in two-dimensional materials.

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

3 major / 2 minor

Summary. The manuscript reports first-principles DFT calculations on bilayer Janus 1T-MnSSe for multiple AA- and AB-type stackings. It identifies the AA2 configuration as the energetic ground state exhibiting A-type antiferromagnetic order, extracts effective Ising exchange parameters from total-energy differences among collinear spin states, performs Monte Carlo sampling to obtain Néel temperatures above 300 K for antiferromagnetic stackings and Curie temperatures up to 250 K for ferromagnetic phases, and identifies several half-metallic ferromagnetic configurations whose spin polarization can be tuned to metallic by carrier doping or biaxial strain.

Significance. If the mapping from DFT energies to the Ising model and the resulting transition temperatures prove robust, the work would demonstrate stacking-tunable interlayer magnetism and room-temperature ordering in a 2D Janus bilayer, offering a concrete platform for spintronic devices that combine half-metallicity with external control via doping and strain.

major comments (3)
  1. [Methods and §3] Methods and §3 (Magnetic Configurations): The Ising parameters are obtained from total-energy differences among a small number of collinear configurations; no additional magnetic configurations, explicit next-nearest-neighbor terms, or biquadratic exchange are reported, leaving open whether longer-range or anisotropic interactions (potentially comparable in magnitude to the fitted J) alter the Monte Carlo transition temperatures by tens of percent.
  2. [§4] §4 (Monte Carlo Simulations): The reported Néel (>300 K) and Curie (up to 250 K) temperatures rest on the effective Ising Hamiltonian; without finite-size scaling, explicit inclusion of single-ion anisotropy from SOC, or direct comparison of DFT energy differences to the Ising predictions for an independent set of spin arrangements, the quantitative reliability of these temperatures cannot be assessed.
  3. [Computational Details] Computational Details: No convergence tests with respect to k-point sampling, plane-wave cutoff, or Hubbard U value are provided, nor is the sensitivity of the extracted exchange parameters to these choices quantified; this directly affects the load-bearing claim that bilayer ordering temperatures exceed those of the monolayer.
minor comments (2)
  1. Figure captions and text should explicitly state the supercell size and number of magnetic configurations used to fit the Ising model.
  2. The abstract states 'nearly 100% spin polarization' while the main text should quantify the actual polarization value at the Fermi level for each half-metallic stacking.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment point by point below.

read point-by-point responses

  1. Referee: [Methods and §3] Methods and §3 (Magnetic Configurations): The Ising parameters are obtained from total-energy differences among a small number of collinear configurations; no additional magnetic configurations, explicit next-nearest-neighbor terms, or biquadratic exchange are reported, leaving open whether longer-range or anisotropic interactions (potentially comparable in magnitude to the fitted J) alter the Monte Carlo transition temperatures by tens of percent.

    Authors: We acknowledge that the effective Ising model is constructed from a limited set of collinear configurations, which is a standard mapping in the 2D-magnet literature. To address the concern, the revised manuscript will include additional spin configurations and a brief discussion of possible next-nearest-neighbor contributions. The dominant nearest-neighbor terms already reproduce the DFT ground-state ordering, supporting the robustness of the main conclusions. revision: partial

  2. Referee: [§4] §4 (Monte Carlo Simulations): The reported Néel (>300 K) and Curie (up to 250 K) temperatures rest on the effective Ising Hamiltonian; without finite-size scaling, explicit inclusion of single-ion anisotropy from SOC, or direct comparison of DFT energy differences to the Ising predictions for an independent set of spin arrangements, the quantitative reliability of these temperatures cannot be assessed.

    Authors: The Ising Hamiltonian reproduces the DFT energies of the fitted configurations by construction. We will add Monte Carlo results for larger lattices to illustrate finite-size behavior and include a short discussion of the expected small SOC anisotropy for Mn 3d systems. A direct validation against an independent set of DFT configurations will also be provided in the revision. revision: partial

  3. Referee: [Computational Details] Computational Details: No convergence tests with respect to k-point sampling, plane-wave cutoff, or Hubbard U value are provided, nor is the sensitivity of the extracted exchange parameters to these choices quantified; this directly affects the load-bearing claim that bilayer ordering temperatures exceed those of the monolayer.

    Authors: We agree that explicit convergence data strengthen the quantitative claims. The revised supplementary material will include tests for k-point density, plane-wave cutoff, and Hubbard U, together with the resulting variation in the extracted J values. These tests confirm that the bilayer-versus-monolayer ordering-temperature trend remains unchanged within the converged parameter range. revision: yes

Circularity Check

1 steps flagged

Néel/Curie temperatures obtained by Monte Carlo on Ising model whose J parameters are fitted directly to the DFT total energies being 'predicted'

specific steps
  1. fitted input called prediction [Abstract (and implied Results/Monte Carlo section)]
    "Monte Carlo simulations based on an effective Ising model reveal enhanced magnetic transition temperatures in the bilayer relative to the monolayer, with Néel temperatures above 300 K for antiferromagnetic stackings and Curie temperatures up to 250 K for ferromagnetic phases."

    The Ising J values are obtained by mapping DFT total energies of selected spin configurations onto the model; the subsequent MC sampling then yields Tc values that are mathematically determined by those fitted J's. The reported transition temperatures therefore reduce to a re-expression of the input DFT energy differences rather than an independent prediction.

full rationale

The paper's headline magnetic transition temperatures are not independent results; they are computed from an effective Ising Hamiltonian whose exchange parameters are extracted from the same first-principles total-energy differences that define the magnetic ground states. This matches the 'fitted input called prediction' pattern. The electronic and stacking claims remain independent of this step, so the circularity is partial rather than total. No self-citation load-bearing or self-definitional steps are evident from the supplied text.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claims rest on standard DFT assumptions for magnetic 2D materials and on the validity of mapping DFT energies to a classical Ising Hamiltonian; no new entities are postulated.

free parameters (1)
  • Ising exchange parameters
    Exchange couplings are extracted from DFT total-energy differences for different spin configurations and then used in Monte Carlo; their numerical values are not stated in the abstract.
axioms (2)
  • domain assumption Density-functional theory with chosen functional and Hubbard correction accurately ranks magnetic states and interlayer energies in MnSSe.
    Invoked implicitly by the use of first-principles calculations to determine ground-state stacking and magnetic order.
  • domain assumption The effective Ising model captures the dominant energetics for finite-temperature magnetism.
    Required to justify Monte Carlo extraction of Néel and Curie temperatures.

pith-pipeline@v0.9.1-grok · 5740 in / 1496 out tokens · 42038 ms · 2026-06-28T00:42:59.314708+00:00 · methodology

discussion (0)

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