Short-range order in the quantum XXZ honeycomb lattice material <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>BaCo</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>PO</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Bibliographic record
Abstract
We present observations of highly frustrated quasi-two-dimensional (2D) magnetic correlations in the honeycomb lattice layers of the ${S}_{\text{eff}} =1/2$ compound $\ensuremath{\gamma}\ensuremath{-}{\mathrm{BaCo}}_{2}{({\mathrm{PO}}_{4})}_{2}$ ($\ensuremath{\gamma}$-BCPO). Specific heat shows a broad peak comprised of two weak kink features at ${T}_{N1}\ensuremath{\sim}6$ K and ${T}_{N2}\ensuremath{\sim}3.5$ K, the relative weights of which can be modified by sample annealing. Neutron powder diffraction measurements reveal short range quasi-2D order that is established below ${T}_{N1}$ and ${T}_{N2}$, at which two separate, incompatible, short range magnetic orders onset: commensurate antiferromagnetic correlations with correlation length ${\ensuremath{\xi}}_{c}=60\ifmmode\pm\else\textpm\fi{}2$ \AA{} (${T}_{N1}$) and in quasi-2D helical domains with ${\ensuremath{\xi}}_{h}=350\ifmmode\pm\else\textpm\fi{}11$ \AA{} (${T}_{N2}$). The ac magnetic susceptibility response lacks frequency dependence, ruling out spin freezing. Inelastic neutron scattering data on $\ensuremath{\gamma}$-BCPO is compared with linear spin wave theory, and two separate parameter regions of the XXZ ${J}_{1}\ensuremath{-}{J}_{2}\ensuremath{-}{J}_{3}$ model with ferromagnetic nearest-neighbor exchange ${J}_{1}$ are favored, both near regions of high classical degeneracy. High energy coherent excitations ($\ensuremath{\sim}10$ meV) persist up to at least 40 K, suggesting strong in-plane correlations persist above ${T}_{N}$. These data show that $\ensuremath{\gamma}$-BCPO is a rare highly frustrated, quasi-2D ${S}_{\text{eff}} =1/2$ honeycomb lattice material which resists long range magnetic order and spin freezing.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".