Plate Nº 13 · recorded October 10, 2026
Chemistry & MaterialsReported finding
Lattice Parameter Outperforms Electron Count in Predicting Magnetism
Three crystal-spacing thresholds at roughly 14.62 and 14.72 Å organize the magnetic states of Au-based Tsai-type approximants better than the conventional electron-count approach.
By Elena Vasquez4 min read702 words
In brief
- Lattice parameter thresholds at roughly 14.72 Å and 14.62 Å separate three magnetic phases (whirling AFM, whirling FM, and spin-glass)
- The study is scheduled for publication in the Journal of the American Chemical Society on September 30, 2026
- The team was led by Assistant Professor Farid Labib (TUS) and Associate Professor Kazuhiro Nawa (Tohoku University), with Professor Ryuji Tamura (TUS)
- The samples were Au-(Al/Ga)-based 1/1 approximant crystals containing terbium, dysprosium, or holmium
- DOI: 10.1021/jacs.6c05709
Three lattice-spacing thresholds at roughly 14.72 Å and 14.62 Å reliably sort the magnetism of Au-based Tsai-type approximant crystals into three distinct states, according to a study scheduled for publication in the Journal of the American Chemical Society on September 30, 2026.
The work, led by Assistant Professor Farid Labib of Tokyo University of Science (TUS) and Associate Professor Kazuhiro Nawa of Tohoku University, along with Professor Ryuji Tamura of TUS, challenges a long-standing assumption in materials chemistry: that the valence-electron concentration per atom, called the e/a ratio, is the best predictor of magnetic behavior in complex intermetallic alloys.
What did the team actually measure?
The researchers synthesized a series of Au-(Al/Ga)-based "1/1" approximant crystals — periodic relatives of quasicrystals, which are solids with ordered but non-repeating atomic patterns. The samples contained one of three rare-earth elements: terbium (Tb), dysprosium (Dy), or holmium (Ho).
Each compound's structure consists of nested atomic shells, with the magnetic rare-earth sitting at the center of a 12-atom icosahedron. The team then measured structural and magnetic properties across the family and found a nearly monotonic inverse correlation between the e/a ratio and the lattice parameter — meaning that as electron count rises, atomic spacing shrinks.
How do the magnetic states differ across samples?
Three ordered magnetic phases emerged in the non-Heisenberg Tsai-type compounds, meaning systems whose atomic moments do not behave like simple classical magnets:
- Whirling antiferromagnetism (AFM), in which neighboring magnetic moments point in opposite directions, appeared at lattice parameters above roughly 14.72 Å.
- Whirling ferromagnetism (FM), with moments aligning in the same direction, occupied the middle range of 14.62–14.72 Å.
- Spin-glass behavior, in which moments freeze into a disordered arrangement without a clear pattern, appeared below 14.62 Å.
The crystal electric field — the electric environment produced by surrounding atoms — generates strong uniaxial magnetic anisotropy, forcing each magnetic moment to favor a specific direction along one axis.
Why does lattice spacing outperform electron count?
In gold-based Tsai-type approximants, the e/a ratio had previously been shown to track the magnetic ground state. But the new study found that this relationship drifts depending on which rare-earth sits at the icosahedral center and which alloy partners are present.
By contrast, the lattice parameter produced a single, sharply defined phase diagram with no such systematic shifts. The compound's spacing between atoms, measured in ångströms (1 Å = 0.1 nanometers), acted as a unified yardstick.
What did the researchers say about the implications?
Labib framed the broader context: "Quasicrystals are among the most unusual materials discovered to date and are expected to exhibit novel magnetic states and quantum phenomena not found in ordinary crystals."
He added: "Until now, there has been no unified guideline for systematically exploring these novel phenomena in quasicrystals and their approximant crystals."
Nawa emphasized the practical payoff. "The unified magnetic phase diagram constructed in this study can serve as a practical roadmap for systematic exploration of new magnetic quasicrystals and approximant crystals exhibiting novel magnetic orders and quantum phenomena," he said.
He added that the diagram can "provide a guideline for designing new magnetic materials with targeted magnetic ground states, opening new opportunities for discovering unconventional magnetism in quasiperiodic and complex intermetallic systems."
What are the limits of the finding?
The thresholds apply specifically to the Au-(Al/Ga) family and to Tsai-type icosahedral compounds. Whether the same lattice-parameter rule transfers to other approximant families or to true quasicrystals, which lack any repeating unit cell at all, remains untested. The work is also limited to three rare-earth elements; expanding to gadolinium, neodymium, and others will clarify whether the thresholds shift.
What happens next?
Because lattice spacing is an experimentally accessible quantity that any X-ray diffraction measurement can provide, the authors expect their phase diagram to guide synthesis. Researchers hunting for new spin textures or quantum behavior in complex alloys can now screen candidates by lattice size before committing to costly growth and magnetic measurements.
The paper, "Lattice Parameter Governs Magnetic Ground State Selection in Tsai-Type Intermetallic Compounds," carries DOI 10.1021/jacs.6c05709.
via Phys.org Physics (Source)
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