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arxiv: 2604.25365 · v1 · submitted 2026-04-28 · ❄️ cond-mat.str-el

Intrinsic magnetotransport and orientation dependent topological Hall effect in EuAuBi

Lipika , Sneh , Shobha Singh , Ralf Koban , Walter Schnelle , Kaustuv Manna This is my paper

Pith reviewed 2026-05-07 15:09 UTC · model grok-4.3

classification ❄️ cond-mat.str-el
keywords EuAuBitopological Hall effectmagnetotransportantiferromagnetic orderingmetamagnetic transitioncrystal orientationtopological semimetalsingle crystal growth
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The pith

Pb flux growth of EuAuBi crystals enables observation of a topological Hall signal in the antiferromagnetic state for current along the c-axis and field perpendicular to it.

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

The paper shows that switching to a Pb flux growth method produces higher-purity, c-axis-oriented single crystals of the magnetic topological semimetal EuAuBi, eliminating the Au2Bi secondary phases common in earlier Bi flux crystals. This improvement permits Hall measurements in a new geometry with current parallel to the c-axis and magnetic field perpendicular to the c-axis. In this configuration a residual Hall contribution appears below the antiferromagnetic ordering temperature inside a narrow field window. The signal lines up with metamagnetic transitions, magnetoresistance anomalies, and an extra feature in the field-dependent specific heat, pointing to direct coupling between the electronic states and the field-driven magnetic changes. The results indicate that crystal orientation must be considered when searching for topological transport features in magnetic semimetals.

Core claim

Stabilization of c-axis-oriented EuAuBi single crystals via Pb flux growth reveals a finite residual Hall contribution below the antiferromagnetic ordering temperature when current flows parallel to the c-axis and the field is applied perpendicular to the c-axis. This contribution, identified as a topological Hall signal, occurs within a narrow magnetic field range and coincides exactly with metamagnetic transitions, anomalies in the magnetoresistance, and an additional feature in the field-dependent specific heat, demonstrating strong coupling between electronic transport and field-induced magnetic reconstructions.

What carries the argument

The residual Hall contribution measured in the I-parallel-to-c, B-perpendicular-to-c geometry, arising from field-induced magnetic reconstructions below the antiferromagnetic ordering temperature.

If this is right

  • The topological Hall contribution is intrinsic to EuAuBi and tied to its antiferromagnetic order.
  • Electronic transport couples directly to field-induced magnetic reconstructions at the metamagnetic transitions.
  • Crystal orientation determines whether topological transport signatures become visible in magnetic semimetals.
  • Suppressing secondary phases through flux choice is required to access the material's true magnetotransport behavior.

Where Pith is reading between the lines

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

  • Growth optimization that removes impurity phases may expose similar orientation-dependent effects in other magnetic topological semimetals that were previously obscured.
  • Repeating the Hall measurements in additional crystal orientations could test whether other components of the Hall response carry topological information.
  • The narrow field window and specific-heat correlation suggest a well-defined magnetic phase whose spin texture could be mapped by complementary probes such as neutron scattering.

Load-bearing premise

The observed residual Hall signal originates from the intrinsic magnetic structure rather than from residual impurities, magnetic domains, or other extrinsic sources.

What would settle it

If the residual Hall signal appears in crystals still containing detectable Au2Bi secondary phases or fails to vanish when the measurement geometry is rotated away from I parallel to c and B perpendicular to c.

Figures

Figures reproduced from arXiv: 2604.25365 by Kaustuv Manna, Lipika, Ralf Koban, Shobha Singh, Sneh, Walter Schnelle.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) Crystal structure of EuAuBi, the blue, pink, view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a) The as-grown rod-shaped crystals (grown using Pb flux) of approximately 2-3 mm are obtained with hexagonal view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. (a) Zero-field cooling (ZFC) and Field-cooled warming (FCW) magnetization curves in the presence of 0.1 T magnetic view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (a) Field-dependent Hall signal view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. (a) Black curve is the experimental data of zero view at source ↗
read the original abstract

We report the growth of high-quality single crystals of the magnetic topological semimetal EuAuBi using a Pb flux method, which effectively suppresses the formation of secondary Au2Bi impurity phases that were prevalent in the previously reported Bi flux grown crystals. This growth optimization enables reliable investigation of the intrinsic physical properties of EuAuBi. Importantly, Pb flux growth stablilizes c axis oriented single crystals, enabling Hall measurements in a previously unexplored geometry. In this configuration (I parallel to c, B perpendicular to c), a finite residual Hall contribution, known as topological Hall signal emerges below the antiferromagnetic ordering temperature and within a narrow magnetic field range. This Hall contribution coincides with the metamagnetic transitions, anomalies in magnetoresistance, and an additional feature in field-dependent specific heat, indicating strong coupling between the electronic transport and field induced magnetic reconstructions. Consequently, these findings underscore the significance of crystal orientation in uncovering topological transport signatures in magnetic semimetals such as EuAuBi.

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 / 3 minor

Summary. The manuscript reports the synthesis of high-quality EuAuBi single crystals via Pb-flux growth, which suppresses Au2Bi secondary phases that plagued prior Bi-flux crystals and yields c-axis-oriented samples. In the previously unexplored geometry with current parallel to the c-axis and magnetic field perpendicular to c, the authors observe a finite residual Hall resistivity below the antiferromagnetic ordering temperature T_N within a narrow field window; this residual is interpreted as a topological Hall signal arising from real-space Berry curvature during metamagnetic transitions. The signal is reported to coincide with anomalies in magnetoresistance and an additional feature in field-dependent specific heat, indicating strong magneto-electronic coupling.

Significance. If the topological assignment holds after rigorous subtraction and artifact exclusion, the work would establish orientation-dependent topological transport in a magnetic topological semimetal and demonstrate how flux-growth optimization can reveal intrinsic behavior previously masked by impurities. It would also provide a concrete example of transport signatures tied to field-induced magnetic reconstructions in antiferromagnetic semimetals.

major comments (3)
  1. [Hall resistivity analysis and Fig. 4 (or equivalent)] The central claim that the residual Hall resistivity is topological rests on the subtraction of normal and anomalous contributions. The manuscript must explicitly detail the fitting procedure (linear normal-Hall term plus M-scaled anomalous term) and show the subtracted curves for the I∥c, B⊥c geometry; without this, it is impossible to rule out residual domain or inhomogeneity contributions that can survive simple subtraction in antiferromagnets.
  2. [Crystal growth and characterization section] The assertion that Pb-flux growth fully eliminates Au2Bi secondary phases (and thereby renders the transport intrinsic) requires quantitative support. Phase-purity quantification via Rietveld-refined powder XRD, EDX elemental mapping, or resistivity residual-ratio comparisons with Bi-flux crystals is needed to substantiate the claim that the observed signal is not influenced by minority phases.
  3. [Magnetotransport measurements and discussion of geometry] In the new I∥c geometry, possible current-jetting or contact-misalignment effects must be addressed. The paper should include field-cooling versus zero-field-cooling comparisons or domain-alignment controls to demonstrate that the narrow-field residual Hall is not an extrinsic artifact of multi-domain states or slight inhomogeneities.
minor comments (3)
  1. [Abstract] Abstract contains a typographical error: 'stablilizes' should read 'stabilizes'.
  2. [Throughout results section] Notation for Hall resistivity components (normal, anomalous, topological) should be defined consistently in the text and figure captions to avoid ambiguity when comparing geometries.
  3. [Specific-heat data] The specific-heat feature coinciding with the Hall signal is mentioned but not quantified (e.g., field position, temperature width); a table or inset overlay would strengthen the correlation claim.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive and detailed report. We address each major comment below and indicate the revisions we will make to strengthen the manuscript.

read point-by-point responses

  1. Referee: [Hall resistivity analysis and Fig. 4 (or equivalent)] The central claim that the residual Hall resistivity is topological rests on the subtraction of normal and anomalous contributions. The manuscript must explicitly detail the fitting procedure (linear normal-Hall term plus M-scaled anomalous term) and show the subtracted curves for the I∥c, B⊥c geometry; without this, it is impossible to rule out residual domain or inhomogeneity contributions that can survive simple subtraction in antiferromagnets.

    Authors: We agree that explicit documentation of the subtraction procedure is essential for the topological Hall interpretation. In the revised manuscript we will add a dedicated subsection describing the linear normal-Hall fit and the M-scaled anomalous term, together with the full set of subtracted ρ_xy curves for the I∥c, B⊥c geometry. These plots will be placed alongside the original data in the relevant figure to allow direct assessment of any residual domain or inhomogeneity contributions. revision: yes

  2. Referee: [Crystal growth and characterization section] The assertion that Pb-flux growth fully eliminates Au2Bi secondary phases (and thereby renders the transport intrinsic) requires quantitative support. Phase-purity quantification via Rietveld-refined powder XRD, EDX elemental mapping, or resistivity residual-ratio comparisons with Bi-flux crystals is needed to substantiate the claim that the observed signal is not influenced by minority phases.

    Authors: The manuscript currently states that Pb-flux growth suppresses Au2Bi phases on the basis of the absence of impurity peaks in single-crystal XRD and the improved residual resistivity ratio relative to Bi-flux crystals. We acknowledge that quantitative metrics would strengthen this claim. In revision we will include Rietveld-refined powder XRD patterns with phase-fraction results and EDX elemental maps confirming the absence of Au2Bi within the detection limit, together with a direct comparison of residual resistivity ratios between the two growth methods. revision: yes

  3. Referee: [Magnetotransport measurements and discussion of geometry] In the new I∥c geometry, possible current-jetting or contact-misalignment effects must be addressed. The paper should include field-cooling versus zero-field-cooling comparisons or domain-alignment controls to demonstrate that the narrow-field residual Hall is not an extrinsic artifact of multi-domain states or slight inhomogeneities.

    Authors: We recognize that the new current-parallel-to-c geometry requires explicit checks for geometric artifacts. In the revised manuscript we will add a paragraph discussing current-jetting and contact-misalignment considerations, supported by measurements performed on multiple contact configurations. We will also present field-cooled versus zero-field-cooled Hall data across the relevant temperature and field range to show that the narrow-field residual signal is reproducible and independent of cooling protocol, thereby ruling out multi-domain or inhomogeneity artifacts. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental observations with independent data support

full rationale

This is an experimental materials physics paper focused on crystal growth optimization (Pb flux vs. prior Bi flux) and direct magnetotransport measurements in a new geometry (I ∥ c, B ⊥ c). The central claim—an orientation-dependent residual Hall signal below T_N coinciding with metamagnetic transitions, MR anomalies, and specific-heat features—is presented as raw and processed measurement data, not as a derived prediction or first-principles result. No equations, parameter fits, or model outputs are shown that reduce the reported signal to the input data by construction. Self-citations (if any) are limited to prior experimental reports on the same compound and do not carry the load-bearing interpretive step. The topological assignment rests on experimental coincidence and subtraction procedures that remain falsifiable against external controls, satisfying the criteria for a self-contained, non-circular report.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work is experimental and draws on standard assumptions of condensed matter physics regarding crystal growth, magnetotransport, and identification of topological Hall signals; no new free parameters, axioms, or invented entities are introduced.

axioms (1)
  • domain assumption Standard assumptions in single-crystal growth and magnetotransport measurements hold, including that flux methods can suppress secondary phases and that Hall signals can be attributed to topological origins when they coincide with magnetic transitions.
    Invoked implicitly in the interpretation of the residual Hall contribution as topological.

pith-pipeline@v0.9.0 · 5482 in / 1282 out tokens · 60755 ms · 2026-05-07T15:09:32.547800+00:00 · methodology

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Reference graph

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