Concept · physics
Magnetism
8 studiesEvidence last moved Sep 27, 2026
Magnetism covers how electron spins order (ferro-, antiferro-, spiral) and how that order couples to charge, light and the lattice. The papers here focus on controlling magnetic order with current, voltage, strain and surface chemistry, and on how magnetic order changes other properties such as excitons and lattice strain.
Antiferromagnets and voltage-controlled magnets are central to low-power spintronics, and students often assume current switches magnets purely through spin torque. These studies show heating, hydrogen loading and strain doing much of the work, and show magnetism reshaping excitons and lattice motion.
Studies
8
Findings
5
8 supporting · 0 challenging · 2 qualifying citations
Open tensions
2
Latest change
Concept page published
Magnetism
Currently
What we know
- Heating near the ordering temperature can be the real switch.
- Magnetic order can be set by an electric gate.
- Antiferromagnetic order responds to local strain and defects.
- Spins shape excitons and the lattice, not only magnetisation.
- Spin-orbit physics creates rich, sometimes topological, spin textures.
Largest unresolved question
Mechanisms are inferred in most control experiments: the Mn3Sn seed layer is not imaged, the hydrogen Fermi-surface mechanism in RKKY multilayers is not measured, and the FePt spin-stress model reproduces data only qualitatively.
Common misconceptions
Current-induced switching of an antiferromagnet is always spin-orbit torque.
In Mn3Sn/W devices switching tracked reaching about 435 K and constant critical power, and torque-only simulations needed far larger currents than observed.
Antiferromagnets are useless because they have no net magnetisation to control.
Their order was reset by strain and gas pressure in haematite membranes and read electrically through the anomalous Hall effect in Mn3Sn.
Magnetism affects only magnetic measurements.
CrSBr's exciton binding changed sharply at its magnetic transition, and demagnetising FePt made its lattice contract.
Related
Claim ledger
What the evidence shows
Drawn from 8 studies in this library. Mix labels say which citation roles are present; they are not a strength score. Supports means evidence for a finding; Challenges means evidence against a stated position; Qualifies marks scope.
Heating near the ordering temperature can be the real switch.
Current-pulse 'spin-orbit torque' switching of the kagome antiferromagnet Mn3Sn happened whenever the device reached about 435 K, near its Néel temperature, and critical power stayed constant with thickness, inconsistent with torque alone; the authors propose a heat-assisted, interface-seeded mechanism.
Magnetic order can be set by an electric gate.
Voltage can switch interlayer coupling: hydrogen loading through a GdOx gate changed RKKY exchange by up to 800 Oe, flipping coupling between ferro- and antiferromagnetic near zero crossings and rotating a free layer by 180° with no field.
- Can a small voltage flip magnetic coupling between thin layers?— Efficiency degraded after about twenty cycles; a holding voltage is needed.
Antiferromagnetic order responds to local strain and defects.
Strain and local chemistry reset antiferromagnetic order: folds in free-standing haematite membranes shifted the Morin transition locally by about 10%, and gas pressure switched order isothermally; removing surface excess iron from Fe1+xTe turned stripe order into a double-q spiral in orthorhombic crystals.
- Can bending a magnetic membrane rewrite its hidden magnetic order?
- Can removing stray iron atoms change a magnet's surface order?
Study Role Design N Population Outcome Can bending a magnetic membrane rewrite its hidden magnetic order? Supports OtherLab experiment: grew and lifted off Rh-doped haematite membranes, imaged antiferromagnetic order with X-ray linear dichroism microscopy across temperature, folds and applied strain, plus finite-element strain modelling. No participant count; results come from a handful of membrane samples of three growth types (A, B, C) imaged in several regions. Free-standing (001) Rh-doped alpha-Fe2O3 (haematite) nanomembranes, about 30 nm thick, with and without oxide buffer layers Local antiferromagnetic (Néel vector) orientation, presence of topological textures, and local Morin transition temperature Can removing stray iron atoms change a magnet's surface order? Supports OtherLow-temperature spin-polarized STM imaging of cleaved Fe1+xTe crystals before and after removing surface excess iron with the tip No participant count; single crystals spanning a range of excess-iron concentrations were imaged Self-flux-grown single crystals of iron telluride with varying excess iron Real-space surface magnetic order (ordering wave vectors, spin orientation) versus excess iron concentration Spins shape excitons and the lattice, not only magnetisation.
Magnetic order feeds back on other degrees of freedom: in CrSBr the excitonic 1s-2p transition shifted from about 50 to 15 meV across the magnetic transition, and in granular FePt films laser demagnetisation caused a transient lattice contraction that returned only after remagnetisation (about 100 ps).
- Can magnetic order switch how excitons behave in a crystal?
- Can magnetic disorder make a metal shrink when it is heated?
Study Role Design N Population Outcome Can magnetic order switch how excitons behave in a crystal? Supports OtherNear-infrared pump, phase-locked mid-infrared probe spectroscopy of a bulk CrSBr flake across temperature and with a small magnetic field, compared with anisotropic many-body calculations. One main 620-nm-thick bulk sample measured across temperatures; no statistical sample size. Bulk flake of the layered van der Waals antiferromagnet CrSBr Intra-excitonic 1s-2p transition energy and linewidth, anisotropy, exciton decay dynamics versus temperature and magnetic field Can magnetic disorder make a metal shrink when it is heated? Supports OtherLab pump-probe experiment: femtosecond laser pulses (single and double) excited granular and continuous FePt films, ultrafast X-ray diffraction tracked out-of-plane strain, MOKE tracked magnetisation, and finite-element models tested the stress picture. No sample count; two thin films (one granular, one continuous) measured over a range of fluences and pulse delays. About 9.5 nm thick L10-ordered FePt films on MgO: a granular film of FePt grains in carbon and a continuous epitaxial film Time-resolved out-of-plane lattice strain, and transient magnetisation Spin-orbit physics creates rich, sometimes topological, spin textures.
Spin-orbit coupling links spin and orbital texture: ARPES on BiTeI showed a Rashba energy near 120 meV with orbital textures that switch from radial to tangential across the Dirac point, and symmetry screening of 1649 magnetic structures predicted 12 room-temperature insulators hosting topological magnons.
- Which real magnets could host topological spin waves at room temperature?— Predictions only; no material measured.
Study Role Design N Population Outcome Is the Rashba spin texture really as simple as textbooks say? Supports OtherSynchrotron ARPES with linear/circular polarisation and resonant photon energies on cleaved BiTeI crystals, compared with first-principles slab calculations. Condensed-matter experiment; no participant or sample count — measurements reproduced on multiple crystals. Te-terminated surface of single-crystal BiTeI, a bulk Rashba semiconductor, measured at low temperature Orbital character and in-plane orbital polarisation of the spin-split conduction subbands versus energy, plus circular-dichroism evidence of out-of-plane spin canting Which real magnets could host topological spin waves at room temperature? Supports Computational / modellingGroup-theoretical screening of magnetic structures in the BCS database followed by linear spin-wave calculations on candidate materials Not a sample-based study; 1649 commensurate magnetic structures were screened, narrowing to 23 room-temperature insulators and 12 final candidates Commensurate magnetic structures in the Bilbao Crystallographic Server (BCS) magnetic database Symmetry indicators of magnon bands after symmetry-breaking perturbations; predicted Weyl magnons or magnon axion insulators
Debates
Tensions and limits
Some items are genuine disagreements on the same question. Others mark different assays, populations, or outcomes.
Mechanisms are inferred in most control experiments: the Mn3Sn seed layer is not imaged, the hydrogen Fermi-surface mechanism in RKKY multilayers is not measured, and the FePt spin-stress model reproduces data only qualitatively.
Mechanisms are inferred in most control experiments: the Mn3Sn seed layer is not imaged, the hydrogen Fermi-surface mechanism in RKKY multilayers is not measured, and the FePt spin-stress model reproduces data only qualitatively.
- How does an electric current flip a thick antiferromagnet?
- Can a small voltage flip magnetic coupling between thin layers?
- Can magnetic disorder make a metal shrink when it is heated?
Study Role Design N Population Outcome How does an electric current flip a thick antiferromagnet? Supports OtherCurrent-pulse switching experiments on sputtered Mn3Sn/W Hall-bar devices read out by anomalous Hall resistance, varying pulse length, fall time, temperature, field and film thickness, plus atomistic LLG simulations No single N; devices with five Mn3Sn thicknesses (30 to 100 nm) under many pulse and field conditions Thin films of the chiral kagome antiferromagnet Mn3Sn with a tungsten spin-current layer Anomalous Hall resistance change, critical switching current density and switching ratio Can a small voltage flip magnetic coupling between thin layers? Supports OtherSputtered Co/Pt–Ru wedge–Co/Pd multilayers with a GdOx proton-conducting gate; polar MOKE hysteresis loops measured before and after gate-voltage pulses at positions along the Ru thickness wedge. Measurements on many gated electrodes along a Ru thickness wedge (39 electrodes for the thickness scans), plus selected devices near RKKY zero crossings; no single sample count. Thin-film magnetic heterostructures with a Ru interlayer 0.4–1.7 nm thick, grown on silicon Interlayer exchange field (sign and size of RKKY coupling) versus Ru thickness and gate voltage; field-free switching of the free layer Can magnetic disorder make a metal shrink when it is heated? Supports OtherLab pump-probe experiment: femtosecond laser pulses (single and double) excited granular and continuous FePt films, ultrafast X-ray diffraction tracked out-of-plane strain, MOKE tracked magnetisation, and finite-element models tested the stress picture. No sample count; two thin films (one granular, one continuous) measured over a range of fluences and pulse delays. About 9.5 nm thick L10-ordered FePt films on MgO: a granular film of FePt grains in carbon and a continuous epitaxial film Time-resolved out-of-plane lattice strain, and transient magnetisation
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Surface versus bulk: spin-polarised STM on Fe1+xTe and ARPES on BiTeI probe only surface layers, so extending conclusions to bulk magnetism rests on arguments, whereas membrane and multilayer studies probe whole films.
Evidence for
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Timeline
How understanding moved
Study years are when the paper was published. Evidence edits are dated changes to this page's claims. Explanations are when PaperFren added a Discovery — not a claim that the science happened that day.
2026
Concept page published
Magnetism
Change log
What changed
Dated edits to this page's evidence: studies added or removed from a claim, claims added or withdrawn, and new explanations tagged here. Rewordings are not listed.
- Concept page published
Papers
8 studies in this library bear on Magnetism, ordered by citations.
- How does an electric current flip a thick antiferromagnet?
Current flips thick Mn3Sn layers not by spin torque alone but by heating them to their ordering temperature and letting a spin current set the interface as they cool, which then templates the whole layer.
- Is the Rashba spin texture really as simple as textbooks say?
In a material with giant Rashba splitting, the electron states mix different atomic orbitals, and each orbital piece carries its own spin pattern, so the simple counter-rotating spin picture is incomplete.
- Can a small voltage flip magnetic coupling between thin layers?
Pumping hydrogen into a metal spacer with a small gate voltage reversibly weakens and shifts the coupling between two magnetic layers, even flipping it from parallel to antiparallel.
- Can magnetic order switch how excitons behave in a crystal?
In the layered magnet CrSBr, antiferromagnetic order traps excitons in single layers as nearly one-dimensional, tightly bound pairs, and destroying that order by heating or a small magnetic field lets them spread and weakens their binding.
- Can magnetic disorder make a metal shrink when it is heated?
In granular FePt, laser heating first makes the crystal contract because disordering the spins pulls the lattice in, and this contraction disappears if the spins are already disordered.
- Can bending a magnetic membrane rewrite its hidden magnetic order?
Thin haematite membranes peeled off their substrates still host whirling antiferromagnetic textures, and bending or stretching them can switch the magnetic state without changing temperature.
- Which real magnets could host topological spin waves at room temperature?
A symmetry-based screen of known magnetic materials identified twelve room-temperature magnetic insulators predicted to host topologically protected spin waves once a field or strain is applied.
- Can removing stray iron atoms change a magnet's surface order?
Stripping the extra iron atoms from the surface of iron telluride with an STM tip switches its magnetic pattern from a single stripe or spiral order to a checkerboard-like double-q order once the crystal lattice is less distorted.
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Questions
What is still open
Mechanisms are inferred in most control experiments: the Mn3Sn seed layer is not imaged, the hydrogen Fermi-surface mechanism in RKKY multilayers is not measured, and the FePt spin-stress model reproduces data only qualitatively.
Surface versus bulk: spin-polarised STM on Fe1+xTe and ARPES on BiTeI probe only surface layers, so extending conclusions to bulk magnetism rests on arguments, whereas membrane and multilayer studies probe whole films.
Study this conceptflashcards and short-answer questions
What evidence suggests that heating, not torque alone, switches Mn3Sn?
Switching always occurred when the device reached about 435 K, near the Néel temperature, regardless of pulse length or starting temperature. Critical current fell with film thickness while critical power stayed constant, and pure torque simulations needed much larger currents. Slow pulse fall times switched better than abrupt ones, consistent with order being reset while cooling through the transition. The authors propose a seeded mechanism, though the seed is not imaged.
How can a gate voltage change magnetic coupling in a metallic multilayer?
In Co/Pt-Ru-Co/Pd stacks with a GdOx gate, voltage drove hydrogen into the structure. This reduced the oscillating RKKY coupling amplitude and shifted its phase, changing the exchange field by up to 800 Oe. Near a zero crossing that flips coupling sign, switching the free layer by 180° without a field. Endurance was limited to around twenty cycles.