Magnetic hysteresis of magnetite at high temperature: grain size variation
Bibliographic record
Abstract
SUMMARY Thermoremanent magnetization (TRM), the primary magnetic memory of igneous rocks, depends for its stability through geologic time on mineral carriers with high coercivities and high unblocking temperatures. The palaeomagnetic record of past magnetic field directions and intensities is the key to unraveling Earth's tectonic history. Yet we still do not fully understand how the familiar mineral magnetite, in the micrometer grain size range typically responsible for stable TRM, acquires and holds its signal. Direct indicators of magnetite remanence-carrying capacity and coercivity at high temperature T are saturation remanence relative to saturation magnetization Mrs/Ms and coercive force Hc. This study is the first to measure the variation of these hysteresis properties for magnetite, from room temperature to the Curie point, across the entire size range from 25 nm to 135 µm, covering superparamagnetic, single-domain, vortex, pseudo-single-domain and multidomain magnetic behaviour. The paper focuses on: (1) Hc(T) and Mrs(T) observations and their reproducibility; (2) mathematical relationships of Hc(T) and Mrs(T) to Ms(T), used in modelling TRM and for unbiased comparisons of thermal variations; (3) the shapes of magnetite grains and the number of domains they contain, revealed by demagnetizing factors N = Hc/Mrs and (4) the grain size dependences of Hc and Mrs at ordinary and elevated T, delineating domain structure changes and mechanisms of coercivity.
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How this classification was reachedexpand
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 | 0.000 |
| 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 teacher head, 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".