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arxiv: 1906.11627 · v1 · pith:NP6LYETInew · submitted 2019-06-27 · ❄️ cond-mat.mtrl-sci

Bulk single crystal growth of the theoretically predicted magnetic Weyl semimetals RAlGe (R = Pr, Ce)

P. Puphal , C. Mielke , N. Kumar , Y. Soh , T. Shang , M. Medarde , J. S. White , E. Pomjakushina This is my paper

Pith reviewed 2026-05-25 14:54 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords single crystal growthmagnetic Weyl semimetalsPrAlGeCeAlGefloating zone techniquespin-glass transitionantiferromagnetic orderpolar crystal structure
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The pith

Floating zone growth produces stoichiometric PrAlGe and CeAlGe crystals that adopt the predicted polar structure but display spin-glass and antiferromagnetic orders instead of the expected ferromagnetism.

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

The paper shows that a floating zone technique succeeds in growing single crystals of PrAlGe and CeAlGe with the intended 1:1:1 composition, while flux methods produce Al-rich samples. Both compounds form in the anticipated polar I4₁md space group. Their low-temperature magnetic behavior deviates from theory: PrAlGe enters a spin-glass-like state below 16 K with easy axis along c, and CeAlGe orders antiferromagnetically below 5 K with easy plane in the ab directions. These crystals supply clean samples for examining how magnetism couples to topological Weyl nodes under applied fields.

Core claim

Both systems with the intended 1:1:1 stoichiometry crystallize in the anticipated polar I4₁md (No. 109) space group, although neither displays the theoretically expected ferromagnetic ground state. Instead PrAlGe displays a spin-glass-like transition below 16 K with an easy-c-axis and CeAlGe has an easy-ab-plane antiferromagnetic order below 5 K. The grown crystals provide an ideal platform for microscopic studies of the magnetic field-tunable correlation physics involving magnetism and topological Weyl nodes.

What carries the argument

The floating zone technique, which grows crystals without a crucible or flux to enforce exact 1:1:1 stoichiometry and the target polar structure.

If this is right

  • The crystals allow direct microscopic probes such as neutron scattering or ARPES to map how the observed magnetic orders modify the Weyl nodes.
  • Field-dependent measurements can test whether the spin-glass or antiferromagnetic states can be tuned to recover ferromagnetic-like behavior near the Weyl points.
  • Comparison of transport data between floating-zone and flux-grown crystals isolates the role of aluminum excess in suppressing the predicted ferromagnetism.

Where Pith is reading between the lines

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

  • If the magnetic transitions prove robust across multiple growth batches, theoretical calculations of the Weyl spectrum must incorporate the actual antiferromagnetic or spin-glass order rather than the assumed ferromagnetism.
  • The polar space group combined with the observed easy-axis or easy-plane magnetism suggests possible electric-field control of the magnetic domains or node positions, a direction not addressed in the growth paper.
  • Extending the floating-zone approach to other RAlGe members could map how rare-earth choice tunes the balance between glassy, antiferromagnetic, and ferromagnetic regimes.

Load-bearing premise

The floating zone method produces crystals whose measured magnetic transitions are intrinsic to perfect 1:1:1 stoichiometry and unaffected by undetected defects or small composition shifts.

What would settle it

Magnetization or resistivity measurements on crystals deliberately grown with controlled 1-2 percent aluminum excess or intentional vacancies that reproduce the spin-glass or antiferromagnetic transitions seen in the floating-zone samples.

Figures

Figures reproduced from arXiv: 1906.11627 by C. Mielke, E. Pomjakushina, J. S. White, M. Medarde, N. Kumar, P. Puphal, T. Shang, Y. Soh.

Figure 1
Figure 1. Figure 1: Extract of DTA curves of polycrystalline CeAlGe [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Pictures of the flux-grown crystals of a) CeAlGe [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: Backscattered x-ray Laue images from the PrAlGe [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Rietveld refinement of the crystal structure pa [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Typical EDS spectra from the surfaces of two [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Low temperature magnetization measured in zero [PITH_FULL_IMAGE:figures/full_fig_p006_7.png] view at source ↗
Figure 10
Figure 10. Figure 10: Temperature dependence of the resistivity with [PITH_FULL_IMAGE:figures/full_fig_p007_10.png] view at source ↗
Figure 9
Figure 9. Figure 9: Field-dependence of the magnetization measured [PITH_FULL_IMAGE:figures/full_fig_p007_9.png] view at source ↗
Figure 12
Figure 12. Figure 12: Temperature dependent AC magnetisation mea [PITH_FULL_IMAGE:figures/full_fig_p008_12.png] view at source ↗
Figure 11
Figure 11. Figure 11: Bulk magnetic property data obtained on a [PITH_FULL_IMAGE:figures/full_fig_p008_11.png] view at source ↗
Figure 13
Figure 13. Figure 13: Field dependent magnetisation measured on a [PITH_FULL_IMAGE:figures/full_fig_p008_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: Temperature dependent resistivity with a cur [PITH_FULL_IMAGE:figures/full_fig_p009_14.png] view at source ↗
read the original abstract

We explore two methods for single crystal growth of the theoretically proposed magnetic Weyl semimetals $R$AlGe ($R$ = Pr,Ce), which prove that a floating zone technique, being both crucible- and flux-free, is crucial to obtain perfectly stoichiometric $R$AlGe crystals. In contrast, the crystals grown by a flux growth technique tend to be Al-rich. We further present both structural and elemental analysis, along with bulk magnetization and electrical resistivity data on the crystals prepared by the floating zone technique. Both systems with the intended 1:1:1 stoichiometry crystallize in the anticipated polar I4$_{1}$md (No. 109) space group, although neither displays the theoretically expected ferromagnetic ground state. Instead PrAlGe displays a spin-glass-like transition below 16 K with an easy-c-axis and CeAlGe has an easy-ab-plane antiferromagnetic order below 5 K. The grown crystals provide an ideal platform for microscopic studies of the magnetic field-tunable correlation physics involving magnetism and topological Weyl nodes.

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

2 major / 2 minor

Summary. The manuscript reports single-crystal growth of PrAlGe and CeAlGe via floating-zone (FZ) and flux methods, asserting that the crucible- and flux-free FZ technique is essential for obtaining perfectly stoichiometric 1:1:1 crystals that crystallize in the polar I4₁md (No. 109) space group. Structural and elemental analyses plus bulk magnetization and resistivity data are presented on the FZ crystals; these show a spin-glass-like transition below 16 K with easy c-axis anisotropy for PrAlGe and easy ab-plane antiferromagnetic order below 5 K for CeAlGe, in contrast to the theoretically predicted ferromagnetic ground state. The crystals are offered as a platform for microscopic studies of magnetic field-tunable correlation physics involving magnetism and Weyl nodes.

Significance. If the stoichiometry claim and the intrinsic character of the observed magnetic states are substantiated, the work supplies high-quality crystals for examining the interplay between magnetism and topological Weyl nodes, which addresses an important experimental bottleneck in magnetic topological semimetals.

major comments (2)
  1. [Elemental analysis section] Elemental analysis section (and abstract): the central claim that FZ growth yields 'perfectly stoichiometric' crystals whose magnetic transitions are intrinsic rests on the assertion that flux crystals are Al-rich while FZ crystals are not; however, no tabulated EDX/WDS/ICP values, standard deviations, spatial homogeneity maps, or detection limits are supplied to quantify deviations below the 0.5–2 at.% thresholds known to alter magnetic ground states in related R-T-X compounds.
  2. [Magnetization and resistivity results] Magnetization and resistivity results: the reported transition temperatures (16 K spin-glass-like for PrAlGe; 5 K AFM for CeAlGe) and anisotropy directions are load-bearing for the claim that the states differ from theory, yet the manuscript provides neither raw data files, error bars on susceptibility or resistivity curves, nor quantitative criteria used to classify the PrAlGe transition as spin-glass-like versus other possibilities.
minor comments (2)
  1. [Abstract] Abstract: inconsistent LaTeX rendering of the space group (I4₁md versus I4_{1}md); standardize notation throughout.
  2. [Introduction] The manuscript would benefit from explicit comparison of the observed magnetic structures to the theoretical predictions cited in the introduction, including any calculated doping sensitivity of the FM state.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comments. We address each major point below and will revise the manuscript accordingly to strengthen the presentation of our data.

read point-by-point responses

  1. Referee: [Elemental analysis section] Elemental analysis section (and abstract): the central claim that FZ growth yields 'perfectly stoichiometric' crystals whose magnetic transitions are intrinsic rests on the assertion that flux crystals are Al-rich while FZ crystals are not; however, no tabulated EDX/WDS/ICP values, standard deviations, spatial homogeneity maps, or detection limits are supplied to quantify deviations below the 0.5–2 at.% thresholds known to alter magnetic ground states in related R-T-X compounds.

    Authors: We agree that quantitative tabulation of the elemental analysis is necessary to fully support the stoichiometry claims. The manuscript does include EDX and WDS measurements showing Al-rich compositions in flux crystals and closer-to-ideal 1:1:1 ratios in FZ crystals, but these were presented only in summary form without tables or error statistics. In the revised version we will add tabulated EDX/WDS values (including standard deviations from multiple spots), details on the number of measurements per crystal, and any available spatial homogeneity information. We will also note the detection limits of the instruments used. revision: yes

  2. Referee: [Magnetization and resistivity results] Magnetization and resistivity results: the reported transition temperatures (16 K spin-glass-like for PrAlGe; 5 K AFM for CeAlGe) and anisotropy directions are load-bearing for the claim that the states differ from theory, yet the manuscript provides neither raw data files, error bars on susceptibility or resistivity curves, nor quantitative criteria used to classify the PrAlGe transition as spin-glass-like versus other possibilities.

    Authors: We accept that the magnetic data require clearer quantitative support. The manuscript reports DC magnetization and resistivity curves that define the transition temperatures and anisotropy directions, but error bars and explicit classification criteria were omitted. In revision we will add error bars to all susceptibility and resistivity plots (derived from multiple measurements or instrument resolution), state the quantitative criteria used to classify the PrAlGe transition as spin-glass-like (e.g., ZFC/FC bifurcation, frequency dependence if AC data exist, or memory effects), and clarify how the AFM order in CeAlGe was identified. Raw data files can be provided as supplementary material or deposited in a public repository. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental report with no derivations or fitted predictions

full rationale

The paper reports crystal growth methods, structural characterization (XRD confirming I4₁md), elemental analysis, and bulk magnetic/resistivity measurements. No equations, theoretical derivations, parameter fits, or predictions are present that could reduce to self-definition or self-citation. Claims rest on standard laboratory techniques and external instruments; the mismatch with theory (no FM order) is presented as an observation, not a derived result. Self-citations, if any, are not load-bearing for any chain. This matches the default expectation of no significant circularity for experimental work.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Experimental crystal growth and characterization paper. No free parameters, mathematical axioms, or invented entities are introduced; all claims rest on standard synthesis and measurement techniques.

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Reference graph

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