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arxiv: 2505.09891 · v2 · pith:NJIPSFJBnew · submitted 2025-05-15 · ❄️ cond-mat.mtrl-sci · cond-mat.mes-hall

Complex electronic topography and magnetotransport in an in-plane ferromagnetic kagome metal

Anup Pradhan Sakhya , Richa Pokharel Madhogaria , Barun Ghosh , Nabil Atlam , Milo Sprague , Mazharul Islam Mondal , Himanshu Sheokand , Arun K. Kumay
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Shirin Mozaffari Rui Xue Yong P. Chen David G. Mandrus Arun Bansil Madhab Neupane
This is my paper

Pith reviewed 2026-05-25 07:45 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci cond-mat.mes-hall
keywords kagome metalDirac coneferromagnetismARPESanomalous Hall effectflat bandmagnetotransporttopological phases
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The pith

The Dirac cone gap in this kagome magnet closes when the magnetic moments align in the plane.

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

This paper examines the electronic and magnetic properties of a ferromagnetic kagome metal. It shows a transition to ferromagnetism at 375 K with in-plane easy axis, along with a Dirac cone and a flat band near the Fermi level observed via ARPES. Calculations indicate that the Dirac cone gap can be tuned by the direction of the magnetic moment, opening to about 15 meV for out-of-plane orientation but remaining closed for in-plane, matching the measurements. This demonstrates how magnetism interacts with the topological features in kagome lattices. A sympathetic reader would care because it suggests a way to control electronic topology through magnetic orientation in these frustrated materials.

Core claim

In this ferromagnetic kagome metal, theoretical calculations show that an out-of-plane magnetic moment opens a gap of approximately 15 meV in the Dirac cone, while an in-plane alignment results in a gapless state that is confirmed by ARPES measurements.

What carries the argument

The magnetic moment orientation that modulates the gap size in the Dirac cone of the Mn kagome lattice.

If this is right

  • The material undergoes a paramagnetic-to-ferromagnetic transition at 375 K with the in-plane direction as the easy magnetization axis.
  • ARPES detects a Dirac cone near the Fermi energy together with a flat band that spans a large portion of the Brillouin zone due to wave-function interference on the kagome lattice.
  • The Hall resistivity contains a substantial anomalous Hall effect contribution arising from the ferromagnetism.
  • Changing the magnetic moment direction switches the Dirac cone between gapped and gapless states.

Where Pith is reading between the lines

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

  • External magnetic fields could be used to switch between gapped and gapless Dirac states in related kagome compounds.
  • The result links magnetic frustration on the kagome lattice to the preservation of gapless Dirac points specifically in the in-plane configuration.
  • The same orientation dependence may appear in other members of the RMn6Sn6 family and could be tested by varying the rare-earth element.

Load-bearing premise

The ARPES spectra accurately reflect the bulk band structure without significant surface reconstruction or inhomogeneity altering the Dirac cone.

What would settle it

An ARPES measurement performed while forcing the magnetization out of plane that shows no 15 meV gap opening at the Dirac point would falsify the modulation claim.

Figures

Figures reproduced from arXiv: 2505.09891 by Anup Pradhan Sakhya, Arun Bansil, Arun K. Kumay, Barun Ghosh, David G. Mandrus, Himanshu Sheokand, Madhab Neupane, Mazharul Islam Mondal, Milo Sprague, Nabil Atlam, Richa Pokharel Madhogaria, Rui Xue, Shirin Mozaffari, Yong P. Chen.

Figure 1
Figure 1. Figure 1: Theoretical modulation of Dirac gap through magnetization [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Observation of in-plane ferromagnetization and the anomalous Hall effect. (a) Temperature dependence of magnetization with an [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Observation of Dirac cone at the K point of the Brillouin zone. (a) ARPES measured Fermi surface (FS) measured along the (001) direction using a photon energy of 92 eV and linear horizontal (LH) polarization. High-symmetry points are labeled in black color. (b) Constant energy contour at a binding energy of - 400 meV. ARPES measured band dispersion along the K–Γ–K high symmetry line at a photon energy of (… view at source ↗
Figure 4
Figure 4. Figure 4: Polarization-dependent behavior of the flat band and Dirac [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
read the original abstract

The intricate interplay between flat bands, Dirac cones, and magnetism in kagome materials has recently attracted significant attention from materials scientists, particularly in compounds belonging to the RMn6Sn6 family (R = Sc, Y, rare earths), due to their inherent magnetic frustration. Here, we present a detailed investigation of the ferromagnetic (FM) kagome magnet ScMn6(Sn0.78Ga0.22)6 using angle-resolved photoemission spectroscopy (ARPES), magnetotransport measurements, and density functional theory (DFT) calculations. Our findings reveal a paramagnetic-to-FM transition at 375 K, with the in-plane direction serving as the easy magnetization axis. Notably, ARPES measurements reveal a Dirac cone near the Fermi energy, while the Hall resistivity exhibits a substantial contribution from the anomalous Hall effect. Additionally, we observe a flat band spanning a substantial portion of the Brillouin zone, arising from the destructive interference of wave functions in the Mn kagome lattice. Theoretical calculations reveal that the gap in the Dirac cone can be modulated by altering the orientation of the magnetic moment. An out-of-plane orientation produces a gap of approximately 15 meV, while an in-plane alignment leads to a gapless state, as corroborated by ARPES measurements. This comprehensive analysis provides valuable insights into the electronic structure of magnetic kagome materials and paves the way for exploring novel topological phases in this material class.

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 / 0 minor

Summary. The manuscript investigates the ferromagnetic kagome metal ScMn6(Sn0.78Ga0.22)6 using ARPES, magnetotransport, and DFT. It reports a paramagnetic-to-ferromagnetic transition at 375 K with in-plane easy axis, a Dirac cone near EF and a flat band in ARPES, anomalous Hall effect in Hall resistivity, and DFT results showing a ~15 meV Dirac gap for out-of-plane magnetization but a gapless state for in-plane magnetization, with the latter stated to match ARPES data.

Significance. If the central claim on magnetic-orientation control of the Dirac gap holds after addressing surface-bulk correspondence, the work adds to the understanding of tunable topological features in magnetic kagome lattices by linking DFT predictions to experimental spectra and transport. The multi-technique approach is standard but the explicit gap modulation result would be a useful addition if robustly supported.

major comments (1)
  1. [Abstract] Abstract (and the ARPES-DFT comparison section): the central claim that ARPES corroborates the gapless Dirac state specifically for in-plane magnetization (contrasted with the 15 meV out-of-plane gap) is load-bearing, yet ARPES is surface-sensitive; without reported checks for surface termination dependence, depth profiling, or possible Sn/Ga sublattice inhomogeneity effects on the apparent gap, the match to bulk DFT cannot be taken as direct corroboration.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments. We address the major concern regarding surface sensitivity of ARPES below, and will revise the manuscript accordingly to strengthen the presentation of the ARPES-DFT comparison.

read point-by-point responses

  1. Referee: [Abstract] Abstract (and the ARPES-DFT comparison section): the central claim that ARPES corroborates the gapless Dirac state specifically for in-plane magnetization (contrasted with the 15 meV out-of-plane gap) is load-bearing, yet ARPES is surface-sensitive; without reported checks for surface termination dependence, depth profiling, or possible Sn/Ga sublattice inhomogeneity effects on the apparent gap, the match to bulk DFT cannot be taken as direct corroboration.

    Authors: We agree that ARPES is surface-sensitive and that explicit validation of surface-bulk correspondence strengthens the central claim. In the revised manuscript we will add a paragraph in the ARPES-DFT section discussing surface termination in the RMn6Sn6 family (citing prior ARPES work on isostructural compounds where spectra align with bulk DFT) and note that the in-plane easy axis is independently established by bulk magnetotransport. We will also state that the nominal Sn/Ga ratio is uniform across the crystal (supported by XRD and transport) with no detected inhomogeneity. To reflect these considerations we will change the abstract wording from “as corroborated by ARPES measurements” to “consistent with ARPES measurements” and add an explicit caveat on the surface nature of the data. These changes address the load-bearing aspect without altering the reported observations. revision: yes

Circularity Check

0 steps flagged

No circularity: claims rest on independent ARPES, transport, and standard DFT

full rationale

The abstract and described derivation chain present the Dirac-cone gap modulation (out-of-plane ~15 meV vs. in-plane gapless) as a direct DFT result, with ARPES serving as external corroboration rather than a fitted input. The paramagnetic-to-FM transition temperature, easy-axis direction, flat-band origin, and anomalous Hall contribution are likewise reported from separate measurements or standard calculations without any equation reducing a reported quantity to a parameter defined from the same dataset. No self-citation is invoked as load-bearing, no ansatz is smuggled, and no renaming of known results occurs. The chain is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The work relies on standard DFT band-structure methods and conventional ARPES interpretation; no new entities are postulated and the only adjustable quantity mentioned is the fixed Ga/Sn ratio of the grown crystal.

free parameters (1)
  • Ga substitution fraction 0.22
    The composition is chosen during crystal growth and is not derived from first principles; it is treated as an input that produces the observed properties.
axioms (1)
  • domain assumption Standard DFT exchange-correlation functional and k-point sampling are sufficient to capture the magnetic and topological features near EF.
    Invoked when comparing calculated gap sizes to ARPES data.

pith-pipeline@v0.9.0 · 5865 in / 1516 out tokens · 23060 ms · 2026-05-25T07:45:17.595353+00:00 · methodology

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