Bibliographic record
Abstract
We have studied thermoremanent magnetization (TRM) produced by fields of 10–140 μT in the (0001) basal plane of a 10 × 6 × 2 mm natural single crystal of hematite, both before and after zero‐field cycling through the Morin transition at TM = 260 K. Stepwise thermal demagnetization of TRM indicated high‐unblocking temperatures between 680°C and the Curie‐Néel temperature TN = 690°C. In contrast, TRM was easily demagnetized by alternating fields, TRM intensity decreasing exponentially with increasing field in typical multidomain fashion. The observed 100‐μT MTRM is 1.1 kA/m. This strong TRM, almost equal to the saturation remanence, results from hematite's weak internal demagnetizing field. Domain walls move almost unhindered to their limiting positions, and TRM intensity approaches saturation. On cooling through TM, spins rotate to the antiferromagnetic c axis, and hematite's weak ferromagnetism is largely lost. However, on reheating in zero field through TM, as the spins rotate back into the basal plane, a “memory” remanence is regenerated in the original TRM direction. This TRM memory was about 25% of MTRM for our crystal and was even more resistant to thermal demagnetization than the original TRM. The 25% memory of TRM is similar to that of 0.12‐ to 0.42‐μm single‐domain hematites. High‐unblocking‐temperature TRM and TRM memory must be due to magnetoelastic pinning of spins in the basal plane by lattice defects, because both TRM and memory decrease with high‐temperature treatment, which anneals out defects. The memory phenomenon seems to be in essence an amplification of residual magnetism that survives below the Morin transition. Remanence produced in a demagnetized sample below TM and room temperature remanence that has been cooled through TM increase in identical ways on warming through the transition. We propose that small regions of canted spins, pinned by crystal defects, remain below TM when the bulk of spins have aligned with the antiferromagnetic c axis. These nuclei serve to regenerate room temperature domain structure and remanence in warming through TM.
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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".