Magnetization of exsolution intergrowths of hematite and ilmenite: Mineral chemistry, phase relations, and magnetic properties of hemo‐ilmenite ores with micron‐ to nanometer‐scale lamellae from Allard Lake, Quebec
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Bibliographic record
Abstract
Hemo‐ilmenite ores from Allard Lake, Quebec, were first studied over 50 years ago. Interest was renewed in these coarsely exsolved oxides, based on the theory of lamellar magnetism as an explanation for the high and stable natural remanent magnetizations (NRMs), 32 to 120 A/m, reported here. To understand the magnetism and evolution of the exsolution lamellae, the microstructures and nanostructures were studied using scanning electron microscopy and transmission electron microscopy (TEM), phase chemistry, and relations between mineral chemistry and the hematite‐ilmenite phase diagram. Cycles of exsolution during slow cooling resulted in lamellae down to 1–2 nm thick. Combined electron microprobe, TEM, and X‐ray diffraction (XRD) results indicate that hematite hosts reached a composition approximately ilmenite (Ilm) 14.4, and ilmenite hosts ∼Ilm 98. The bulk of the very stable NRM, which shows thermal unblocking ∼595–620°C, was acquired during final exsolution in the two‐phase region canted antiferromagnetic R c hematite + R ilmenite. Hysteresis measurements show a very strong anisotropy, with a stronger coercivity normal to, than parallel to, the basal plane orientation of the lamellae. Magnetic saturation (M s ) values are up to 914 A/m, compared to 564 A/m predicted for a modally equivalent spin‐canted hematite corrected for ∼15% R 2+ TiO 3 substitution. Low‐temperature hysteresis, AC‐susceptibility measurements, and Mössbauer results indicate a Néel temperature (T N ) of the geikielite‐substituted ilmenite at ∼43 K. The low‐temperature hysteresis and AC‐susceptibility measurements also show a cluster‐spin‐glass‐like transition near 20 K. Below T N of ilmenite an exchange bias occurs with a 40 mT shift at 10 K.
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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 | 0.000 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it