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Record W1838959485 · doi:10.1002/2013jb010739

Hysteresis and coercivity of hematite

2014· article· en· W1838959485 on OpenAlex

Why this work is in the frame

A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.

affAt least one author lists a Canadian institution in the pinned OpenAlex snapshot.
fundA Canadian funder is recorded on the work.

Bibliographic record

VenueJournal of Geophysical Research Solid Earth · 2014
Typearticle
Languageen
FieldBiochemistry, Genetics and Molecular Biology
TopicGeomagnetism and Paleomagnetism Studies
Canadian institutionsUniversity of Toronto
FundersNatural Sciences and Engineering Research Council of CanadaUniversity of MinnesotaW. M. Keck FoundationEarth Sciences DivisionNational Science Foundation
KeywordsCoercivityRemanenceMagnetocrystalline anisotropyMaterials scienceHematiteCondensed matter physicsSaturation (graph theory)Magnetic anisotropyHysteresisNucleationMagnetizationAnisotropyNuclear magnetic resonanceChemistryMetallurgyMagnetic fieldPhysicsOptics

Abstract

fetched live from OpenAlex

Abstract In room‐temperature hysteresis, 14 submicron hematites (0.12‐0.45 µm) had large coercive forces H c (150‐350 mT), while 22 natural 1‐5.5 mm hematite crystals had H c = 0.8‐23 mT (basal‐plane measurements). Single‐domain (SD) and multidomain (MD) hematites owe their high H c mainly to magnetoelastic anisotropy, caused in fine particles by internal strains and in large crystals by defects like dislocations, with a smaller contribution by triaxial magnetocrystalline anisotropy. A strong correlation between H c and the defect moment M d measured below hematite's Morin transition also favors magnetoelastic control. Saturation remanence/saturation magnetization ratios M rs / M s and coercivity ratios H cr / H c ( H cr is remanent coercive force) are distinctive: M rs / M s = 0.5‐0.9, H cr / H c = 1.02‐1.17 for MD hematites; M rs / M s = 0.5‐0.7, H cr / H c = 1.45‐1.62 for SD hematites. In high‐temperature (20‐690°C) hysteresis, H c ( T ) ~ M s ( T ) to a power 1.8‐2.4 above 385°C. Magnetoelastic wall pinning by crystal defects is thus more likely than control by domain nucleation which depends on magnetocrystalline anisotropy. Our results compare well with existing H c vs. crystal size d data. A suggested peak in H c around 15 µm and a proposed slope change around 100 µm are both questionable. Using only near‐saturation data, H c varies continuously as d −0.61 from ≈0.1 µm to 2 mm. The SD threshold size d 0 may be >15 µm but there is no strong evidence that d 0 ≈100 µm. Direct domain observations are needed to settle the question. Augmented data sets for H c and M rs vs. d show that SD hematite is increasingly affected by thermal fluctuations below ≈0.3 µm and generally confirm a superparamagnetic threshold size d s of 0.025‐0.03 µm.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.

Full frame distilled prediction

Teacher imitation

Not 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.

metaresearch head score (Codex)0.001
metaresearch head score (Gemma)0.001
Version: codex-gemma-dda1882f352aValidation status: machine_predicted_unvalidated
Candidate categoriesnone
Consensus categoriesnone
DomainCandidate signal: none · Consensus signal: none
Study designCandidate signal: Bench or experimental · Consensus signal: none
GenreCandidate signal: Empirical · Consensus signal: Empirical
Teacher disagreement score0.769
Threshold uncertainty score0.289

Codex and Gemma teacher scores by category

CategoryCodexGemma
Metaresearch0.0010.001
Meta-epidemiology (narrow)0.0000.000
Meta-epidemiology (broad)0.0000.000
Bibliometrics0.0000.000
Science and technology studies0.0000.000
Scholarly communication0.0000.000
Open science0.0000.000
Research integrity0.0000.000
Insufficient payload (model declined to judge)0.0000.000

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.

Opus teacher head0.023
GPT teacher head0.320
Teacher spread0.298 · how far apart the two teachers sit on this one work
Validation statusscore_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it