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Magnetism and spintronics

Which real magnets could host topological spin waves at room temperature?

Karaki MJ, Yang X, Williams AJ, et al. · Science advances · 2023

Open access · cc by · source: Europe PMC

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.

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Study at a glance

Design
Computational / modelling — Group-theoretical screening of magnetic structures in the BCS database followed by linear spin-wave calculations on candidate materials
N
Not a sample-based study; 1649 commensurate magnetic structures were screened, narrowing to 23 room-temperature insulators and 12 final candidates
Population
Commensurate magnetic structures in the Bilbao Crystallographic Server (BCS) magnetic database
Outcome
Symmetry indicators of magnon bands after symmetry-breaking perturbations; predicted Weyl magnons or magnon axion insulators

Structured fields used in claim comparison tables when every cited study has a complete layer.

Key findings

Of 1649 commensurate structures, 1171 passed both symmetry filters; among those, 23 were room-temperature magnetic insulators, and 12 were predicted to host Weyl magnons or magnon axion insulators. For the rare-earth perovskites such as TbFeO3, splitting a fourfold degeneracy with a field or strain forces an odd inversion indicator, so Weyl magnons appear regardless of the detailed spin model. In hematite, a magnetic field along [010] was predicted to create Weyl magnons using exchange parameters taken from neutron-scattering fits.

Methodology

The authors mapped spin-wave (magnon) bands onto an equivalent electronic problem so that topological quantum chemistry and symmetry indicators could be used. They filtered magnetic space groups and Wyckoff positions for symmetry-protected magnon degeneracies that split into topologically nontrivial bands when an electric field, magnetic field or strain lowers the symmetry. They applied the filters to the whole magnetic structure database, focused on insulators ordering above room temperature, and confirmed predictions with Heisenberg-type spin-wave models, highlighting TbFeO3 and hematite (α-Fe2O3).

Limitations

No material was measured; these are predictions awaiting experiments such as inelastic neutron scattering. The symmetry method says whether a topological gap exists but not how large it is, so thermal broadening and magnon–magnon interactions at room temperature could wash the effect out. Disorder is not modelled, and only materials with transition temperatures above 300 K were searched, not the full database.

How this study connects

Role on claims

Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.

  • SupportsMagnetismconcept

    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.

    Evidence for the claim as stated.

  • QualifiesMagnetismconcept

    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.

    Scope note — Predictions only; no material measured.

    Limits the claim's scope: a different population, assay, or outcome.

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