First-order ferroelastic transition in a magnetoelectric multiferroic: CuCrO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:math>
Bibliographic record
Abstract
We present the magnetic phase diagram of the multiferroic geometrically frustrated antiferromagnet CuCrO${}_{2}$ determined using dielectric constant and ultrasonic velocity measurements with the magnetic field parallel to the $[1\overline{1}0]$ direction. According to these measurements, at zero field the magnetoelectric phase induced by a proper screw magnetic ordering is observed below ${T}_{N1}=23.4$ K, while the velocity measurements reveal another transition at ${T}_{N2}=24.3$ K. As the dielectric and velocity measurements were performed simultaneously, our results confirm the presence of an intermediate nonferroelectric magnetic state between the magnetoelectric and paramagnetic phases. Moreover, our observations indicate that this intermediate phase persists up to 7 T for a field applied along the $[1\overline{1}0]$ direction. Based on similar observations obtained on the multiferric compounds CuO and MnWO${}_{4}$, this intermediate state is most likely a collinear antiferromagnetic phase. Apart from two phases observed at zero field, the ultrasonic velocity measured in the magnetoelectric phase as a function of the magnetic field reveals a spin-flop transition at ${H}_{\mathrm{flop}}=5$ T at 23 K, which is attributed to the flop of the spin spiral from the (110) plane to the $(1\overline{1}0)$ plane. In this paper, we also present a detailed analysis of the elastic properties of CuCrO${}_{2}$. The analysis of the data using a Landau-type free energy indicates that CuCrO${}_{2}$ undergoes a first-order pseudoproper ferroelastic transition leading to a $\overline{3}m\ensuremath{\rightharpoonup}2/m$ structural transition at ${T}_{N2}$. According to the model, the order parameter of the ferroelastic-antiferromagnetic transition at ${T}_{N2}$ belongs to the ${E}_{g}$ irreducible representation of the trigonal $\overline{3}m$ point group, and the magnetic moments must act as a secondary order parameter.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".