Angular variation of the magnetic properties and reversal mode of aligned single‐domain iron nanoparticles
Bibliographic record
Abstract
We report magnetic hysteresis and back‐field demagnetization data measured at 10° intervals of the angle ψ between the applied field H and the long (magnetically easy) axes of aligned elongated single‐domain iron particles electrodeposited in regularly spaced surface pores in an Al substrate. Our three samples have identical particle diameters, d = 17 nm, but varying axial ratios l / d and spacings d c . Measured hysteresis loops resemble “hysterons” predicted by fanning, curling, and coherent rotation models of magnetization reversal, except for two features. For ψ = 0–60°, particle magnetizations do not reverse simultaneously at a single critical field: distributed particle coercivities produce steep but nonvertical loop segments. Broadened ψ = 80–90° loops indicate imperfectly aligned particles. Comparing coercive force H c ( ψ ) with theoretical variations for different angular dispersions of axes and M rs / M s data with a theoretical cos ψ variation, we find a variance of 6–8.5° in particle alignment. The H c ( ψ ) results most closely resemble the theoretical variation for fanning rotations when ψ ≤ 50° and coherent rotations when ψ > 50°. A predicted hump in the H c ( ψ ) curve at intermediate angles marking the changeover from one mechanism to the other is suppressed by particle interactions (packing factors p of 0.127–0.373). Remanent coercive force measurements H cr ( ψ ) show that irreversible changes, unlike reversible rotations, are incoherent at both large and small ψ . H cr continues to rise, to a high of 340–430 mT, as ψ → 90°, whereas H c ( ψ ) decreases over the same range. H cr ( ψ ) results at large ψ favor fanning reversals for one sample and curling reversals for the other two. A Day plot of M rs / M s versus H cr / H c data gives a novel and distinctive trend from which ψ can determined within ±5° for aligned uniaxial particles.
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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 | 0.001 |
| 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 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".