Chemical Control of the Néel Temperature and Magnetic Anisotropy in the Brownmillerites Ca<sub>2</sub>Fe<sub>2–<i>x</i></sub>Mn<sub><i>x</i></sub>O<sub>5</sub>, <i>x</i> = 0.10–0.25
Bibliographic record
Abstract
Brownmillerite oxides with the composition Ca 2 Fe 2– x Mn x O 5 had been investigated previously for the limited range x = 0.5 to 1.0. Mn 3+ preferentially occupies the octahedral site. This substitution has a strong impact on the magnetic properties as the magnetic ordering temperature, T N, is suppressed from 730 K for x = 0.0 to 465 K for x = 0.5 and the magnetic structure changes from G x ( x = 0.0) to G y ( x = 0.5–1.00). In this study, the compositions x = 0.10 and 0.25 are investigated using single-crystal X-ray and neutron diffraction methods. It is found that T N decreases linearly from x = 0.0 to x = 0.5, with values of 584(2)K for x = 0.25 and 684(2)K for x = 0.1. This behavior is rationalized in terms of a competition between antiferromagnetic and ferromagnetic exchange pathways in the perovskite layers involving Fe 3+ –Fe 3+ and Fe 3+ –Mn 3+ interactions. Profound changes in the magnetic anisotropy also occur as for both x = 0.25 and x = 0.1, the magnetic structure is neither G x or G y, but the moments lie between the a and b axes over nearly the entire temperature range. It has been shown that enhanced dielectric parameters are associated with another brownmillerite oxide, Ca 2 FeCoO 5, in which nonaxial magnetic anisotropy is found within a narrow temperature range, 120–250 K. In the materials prepared in this study, this behavior should be evident at ambient temperature and over a wide temperature range.
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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".