ferromagnetism
Enable an agent to recognise ferromagnetic order, assess its condition and evidence, and decide which magnetic interventions are justified under specified conditions.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an agent to recognise ferromagnetic order, assess its condition and evidence, and decide which magnetic interventions are justified under specified conditions.
Ferromagnetism is a cooperative magnetic ordering in which a material's atomic magnetic moments align spontaneously over macroscopic domains below a Curie temperature, producing a large spontaneous magnetization that can remain after an applied field is removed.
It can be Evaluate whether observations support ferromagnetic order and identify the next discriminating measurement.; Compare magnetic states only after aligning temperature, field, geometry, normalization and measurement history.; Select a magnetization or reversal protocol consistent with measured anisotropy and hysteresis.; Select a demagnetization protocol and verify reduced net magnetization without claiming that magnetic order was removed.; Bound magnetic-state retention across proposed temperature, field and time conditions.; Detect when a changed response requires reassessing domain state, magnetic order or the host material..
Distinguishing features
Test for spontaneous magnetic order rather than inferring ferromagnetism from magnetization observed only under an applied field; record how domain cancellation affects the observation.
Distinguish a demagnetized domain configuration from loss of ferromagnetic order: near-zero specimen magnetization alone does not establish absence of order.
Resolve magnetic sublattice alignment where relevant: uncompensated opposing sublattices support a ferrimagnetic interpretation rather than a ferromagnetic one.
Do not treat hysteresis or remanence alone as decisive identification; test competing explanations, including blocked particles and mixed magnetic phases.
For small particles, distinguish internal magnetic order from stability of the particle's net moment over the observation time.
Scope
+ Evidence for spontaneous ferromagnetic order and its distinction from a specimen's net magnetization
+ Conditions under which ferromagnetic order exists, changes or disappears
+ Domain configuration, anisotropy and dependence on magnetic history
+ Magnetization response, hysteresis and relaxation under specified measurement conditions
+ Actions that alter magnetic state and the evidence needed to verify their outcomes
- Complete chemical composition, crystal structure and fabrication history, owned by material and specimen models
- Magnetostatic field geometry and electromagnetic circuit design
- Complete models of paramagnetism, antiferromagnetism, ferrimagnetism and superconductivity
- Electrical, thermal and mechanical behaviour except where it conditions ferromagnetic order or response
- Device architecture, application performance and system safety certification
Characteristics
- Ordering classification
- ferromagnetic-supported | competing-order-supported | mixed | unresolved Separates demonstrated order from a label inferred from a bulk magnetic signal.
- Magnetic host and extent
- identified specimen, phase, region or particle population Locates the phenomenon and prevents attributing a minority phase's response to the entire specimen.
- Temperature
- K, with uncertainty and equilibration conditions Conditions the existence of order and the interpretation of magnetic response.
- Applied and estimated internal magnetic field
- H in A/m, vector or direction specified; internal-field estimate states the demagnetizing correction Relates response to the field experienced by the material and supports comparisons between specimen geometries.
- Magnetization
- A/m, with direction, normalization volume and field-temperature history Describes the observed magnetic state without confusing net response with microscopic order.
- Ordering transition temperature
- K or an unresolved interval, with transition criterion and method Bounds the conditions over which ferromagnetic order is supported.
- Domain configuration
- single-domain | multidomain | spatially heterogeneous | unresolved, with observation scale Helps explain net magnetization, reversal pathways and effects of demagnetization.
- Magnetic anisotropy
- preferred directions and, where established, anisotropy energy density in J/m³ Constrains stable orientations and the fields needed to reorient magnetization.
- Hysteresis descriptors
- remanent magnetization in A/m and coercive field in A/m, with loop definition, range, orientation and sweep rate Characterises retention and reversal for a particular protocol rather than as unconditional material constants.
- Magnetic relaxation timescale
- s or bounded interval, with temperature, field and fitting method Determines whether an observed magnetic state persists long enough for the proposed use.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 11 findings · 21 questions.
Order identification Establish what magnetic order is present and which material region carries it.
A bulk magnetic signal can have several origins and is insufficient by itself to identify ferromagnetism.
Carrier attribution
Connect the magnetic evidence to an identified phase, region or population.
Magnetic carrier
Record the supported extent of the ferromagnetic contribution and unresolved alternative origins.
- Which phase, region or particle population is supported as carrying the proposed ferromagnetic order? definition
- What measurements and specimen records distinguish its signal from contamination or minority magnetic phases? provenance
Order discrimination
Assess evidence that distinguishes ferromagnetic order from competing interpretations.
Ordering evidence
Record the basis for classifying order beyond attraction, remanence or hysteresis alone.
- What evidence supports spontaneous ferromagnetic order despite possible cancellation between domains? measurement
- Which observations distinguish ferromagnetic alignment from ferrimagnetic, canted antiferromagnetic or field-induced responses? boundary
Ordering conditions Bound the conditions under which the identified ferromagnetic order is supported.
Order and measured magnetic state depend on conditions, and their different boundaries must remain distinguishable.
Thermal order boundary
Characterise temperature-dependent order and the evidence for its transition.
Transition assessment
Record how an ordering transition was identified and what uncertainty remains.
- What temperature interval and measurement criterion locate the loss or onset of ferromagnetic order? measurement
- How were loss of order, particle blocking and irreversible material alteration distinguished? boundary
Nonthermal condition dependence
Relate magnetic order to relevant field, pressure, strain and dimensional conditions.
Supported condition envelope
Identify tested conditions and distinguish changes in order from changes in domain alignment.
- Across which fields, pressures, strains, thicknesses or particle sizes has the ordering classification been tested? measurement
- Which observed changes indicate a different magnetic phase, and which are consistent with rearrangement within the same ordered phase? boundary
Domains and anisotropy Explain how local magnetic order produces the observed spatial and net magnetic state.
Ferromagnetic order can persist across very different net magnetizations and reversal behaviours.
Domain organisation
Record supported domain configurations and their observational limits.
Domain state evidence
Connect spatial observations or qualified inferences to net magnetization.
- What domain configuration is observed or inferred, and at what spatial resolution? measurement
- Can low net magnetization be explained by opposing domains, and what evidence would test that explanation? boundary
Orientation and reversal
Identify preferred orientations and supported mechanisms of magnetic reversal.
Anisotropy and pinning
Record orientation dependence and evidence for rotation, domain-wall motion or pinning.
- Which magnetization directions are preferred relative to crystal axes, specimen shape and applied stress? measurement
- What evidence supports domain-wall motion, magnetization rotation or pinning as controlling reversal? provenance
Response and memory Characterise field-dependent response and persistence under explicit protocols.
Magnetic response and retention cannot be interpreted reliably without history, field conventions and timescale.
Field response
Record comparable magnetization curves and their measurement limitations.
Hysteresis protocol
Attach loop descriptors to preparation, geometry, field range and acquisition conditions.
- What preparation, temperature, orientation, sweep rate and field range produced the measured magnetization loop? provenance
- How were normalization, background subtraction, demagnetizing fields and attainment of saturation assessed? measurement
Time-dependent retention
Distinguish a persistent magnetic state from a response that changes over the observation window.
Relaxation and blocking
Record magnetic-state decay and its implications for interpreting particle populations.
- How does magnetization change after field removal or a field step over the timescale relevant to use? measurement
- For particles, does apparent loss of remanence indicate moment relaxation while internal magnetic order remains? boundary
Magnetic state interventions Connect desired magnetic changes to supported procedures and outcome checks.
An agent must distinguish changing domain state from changing magnetic order or altering the host material.
State setting
Support magnetization, reversal and demagnetization decisions using measured behaviour.
Field treatment selection
Record the desired state, applicable field procedure and verification criterion.
- Which field magnitude, orientation and sequence are supported for setting, reversing or reducing net magnetization? action
- What post-treatment measurement will establish the target state and its required retention? measurement
Condition excursions
Assess magnetic recovery and host changes following thermal or other condition changes.
Recovery and reassessment
Record whether an intervention restores order, changes magnetic history or requires renewed material identification.
- What evidence supports magnetic-state recovery after the proposed temperature, stress or field excursion? action
- Which signs of phase transformation, oxidation or microstructural change require reassessing the magnetic carrier? boundary
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- soft ferromagnets (low-coercivity Fe, Fe-Si, Ni-Fe, used for transformers and motors)
- hard ferromagnets / permanent magnets (high-coercivity Nd-Fe-B, Sm-Co, Alnico, ferrites)
- elemental 3d ferromagnets (Fe, Co, Ni at room temperature)
- rare-earth and 4f ferromagnets (Gd, Dy, and related compounds)
- Heusler and intermetallic ferromagnets
- ferrimagnetic oxides used as practical 'ferrites' (distinct sublattice compensation, often grouped with ferromagnets in engineering)
- itinerant (band) ferromagnets versus localized-moment ferromagnets
- two-dimensional and van der Waals ferromagnets (e.g. CrI3, Fe3GeTe2)
- Which of these kinds and varieties hold for the sense of ferromagnetism this model covers, and on what evidence? provenance
Sources
- Ferromagnetism - Definition of spontaneous magnetization, Curie temperature, domains, hysteresis, and distinction from para-/antiferro-/ferrimagnetism; elemental Fe, Co, Ni; soft vs hard magnets.
What the second pass must settle
- What minimum evidence should qualify an entry as ferromagnetic-supported when microscopic magnetic-structure measurements are unavailable?
- Should weak ferromagnetism from canted antiferromagnetic order be owned here or represented through a neighbouring order model?
- How should mixed ferromagnetic and ferrimagnetic phases be represented when their contributions cannot be separated experimentally?
- What operational criteria should distinguish ordering and blocking boundaries in finite particles, thin films and nonequilibrium specimens?
- Which application-specific tolerances should define successful demagnetization, stable retention and acceptable recovery after condition excursions?