Quasicrystals (QCs) have a unique atomic arrangement that lacks periodicity, giving them unusual symmetries not found in regular crystals. Scientists have been exploring their quasiperiodic magnetic properties and potential uses in spintronics and magnetic cooling areas.
Recently, researchers identified ferromagnetism in gold-gallium-rare earth (Au-Ga-R) icosahedral quasicrystals (iQCs). This finding wasn’t unexpected, as ferromagnetism can occur without periodicity. However, antiferromagnetism, another key type of magnetic order, is more dependent on crystal symmetry and hasn’t been observed in quasicrystals—until now.
In a breakthrough, a team led by Ryuji Tamura from Tokyo University of Science discovered antiferromagnetism in a quasicrystal for the first time, marking a major milestone in understanding quasicrystal behavior.
Building on their earlier discovery of ferromagnetism in Au-Ga-R quasicrystals, researchers uncovered a new Tsai-type gold-indium-europium (Au-In-Eu) quasicrystal with unique rotational symmetries (five-fold, three-fold, and two-fold). They studied its magnetic properties through detailed measurements and experiments.
A novel way to switch antiferromagnetism on and off
Magnetic susceptibility tests revealed a distinct cusp at 6.5 Kelvin (K), signaling an antiferromagnetic transition. Specific heat measurements confirmed this transition, linking the cusp to long-range magnetic order.
To solidify their findings, the team conducted neutron diffraction studies at 10 K and 3 K. At 3 K, they detected magnetic Bragg peaks—clear signs of an ordered magnetic structure—which showed a sharp change near the 6.5 K transition. This marked the first definitive evidence of long-range antiferromagnetic order in a quasicrystal.
The researchers discovered that the Au-In-Eu quasicrystal hosts an antiferromagnetic phase due to its unique positive Curie-Weiss temperature, unlike most previously studied quasicrystals, which typically have negative Curie-Weiss temperatures.
Interestingly, by slightly increasing the electron-per-atom ratio through elemental substitution, the antiferromagnetic phase vanishes, and the quasicrystal exhibits spin-glass behavior, similar to earlier quasicrystals. This finding suggests that a positive Curie-Weiss temperature promotes antiferromagnetic order, paving the way for future research into creating new antiferromagnetic quasicrystals by adjusting electron-per-atom ratios.
This discovery solves the long-standing question of whether real quasicrystals can exhibit antiferromagnetic order. The transformative potential of antiferromagnetic quasicrystals could lead to innovations such as ultrasoft magnetic responses, revolutionizing spintronics, and magnetic refrigeration.
Journal Reference:
- R. Tamura et al. Observation of antiferromagnetic order in a quasicrystal, Nature Physics (2025). DOI: 10.1038/s41567-025-02858-0
