Structural Origin of the Anomalous Temperature Dependence of the Local Magnetic Moments in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>CaFe</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>As</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Family of Materials
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Bibliographic record
Abstract
We report a combination of Fe $K\ensuremath{\beta}$ x-ray emission spectroscopy and density functional reduced Stoner theory calculations to investigate the correlation between structural and magnetic degrees of freedom in ${\mathrm{CaFe}}_{2}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{2}$. The puzzling temperature behavior of the local moment found in rare earth-doped ${\mathrm{CaFe}}_{2}{\mathrm{As}}_{2}$ [H. Gretarsson et al., Phys. Rev. Lett. 110, 047003 (2013)] is also observed in ${\mathrm{CaFe}}_{2}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{2}$. We explain this phenomenon based on first-principles calculations with scaled magnetic interaction. One scaling parameter is sufficient to describe quantitatively the magnetic moments in both ${\mathrm{CaFe}}_{2}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{2}$ ($x=0.055$) and ${\mathrm{Ca}}_{0.78}{\mathrm{La}}_{0.22}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ at all temperatures. The anomalous growth of the local moments with increasing temperature can be understood from the observed large thermal expansion of the $c$-axis lattice parameter combined with strong magnetoelastic coupling. These effects originate from the strong tendency to form As-As dimers across the Ca layer in the ${\mathrm{CaFe}}_{2}{\mathrm{As}}_{2}$ family of materials. Our results emphasize the dual local-itinerant character of magnetism in Fe pnictides.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.005 |
| Meta-epidemiology (narrow) | 0.002 | 0.003 |
| Meta-epidemiology (broad) | 0.001 | 0.004 |
| Bibliometrics | 0.001 | 0.004 |
| Science and technology studies | 0.002 | 0.007 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.008 | 0.005 |
| Research integrity | 0.003 | 0.004 |
| Insufficient payload (model declined to judge) | 0.853 | 0.003 |
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 it