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 dc. 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 Hc(ψ) with theoretical variations for different angular dispersions of axes and Mrs/Ms data with a theoretical cos ψ variation, we find a variance of 6–8.5° in particle alignment. The Hc(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 Hc(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 Hcr(ψ) show that irreversible changes, unlike reversible rotations, are incoherent at both large and small ψ. Hcr continues to rise, to a high of 340–430 mT, as ψ → 90°, whereas Hc(ψ) decreases over the same range. Hcr(ψ) results at large ψ favor fanning reversals for one sample and curling reversals for the other two. A Day plot of Mrs/Ms versus Hcr/Hc 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 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".