Researchers at Tokyo University of Science have synthesized the first bulk, stable ferromagnetic quasicrystals without rapid quenching, resolving a structural instability that has limited magnetism research in these materials.
Quasicrystals are ordered but non repeating structures with unconventional rotational symmetries. Scientists only confirmed ferromagnetism in gold based icosahedral quasicrystals a few years ago, establishing them as a third platform for magnetism alongside periodic crystals and amorphous materials. Every sample since then had to be made through rapid quenching, a process that left the crystals metastable and structurally imperfect. That made it difficult to study their intrinsic magnetic behavior, particularly how they behave near a magnetic phase transition.
The team, led by Professor Ryuji Tamura and Dr. Farid Labib, used a machine learning based phase classifier trained on the quasicrystal database HYPOD-X to screen 675 candidate alloy systems. Gold copper aluminum indium systems containing gadolinium, terbium or dysprosium emerged as the strongest candidates. The researchers synthesized three versions of these quinary alloys using conventional arc melting followed by controlled annealing rather than quenching.
“We developed ferromagnetic icosahedral QCs with unprecedented structural quality,” said Tamura. Annealing the samples at 723 Kelvin for extended periods produced far sharper quasiperiodic order in X ray diffraction tests than earlier quenched versions, and the crystals stayed stable under prolonged heat.
Magnetic and specific heat measurements confirmed bulk, long range ferromagnetic order in all three alloys, with transition temperatures ranging from 9.7 to 28.3 Kelvin depending on which rare earth element was used. The terbium and dysprosium based crystals showed critical behavior close to mean field predictions, consistent with long range magnetic interactions. The gadolinium based version instead showed shorter range interactions, which the team attributed to stronger spin fluctuations in that element.
The result builds on work Tamura’s lab began in 2021, when it first reported long range ferromagnetic order in icosahedral quasicrystals with international collaborators at Tohoku University and Australia’s national nuclear research organization. That discovery could not be fully characterized because the samples were structurally unstable. The new bulk synthesis method removes that barrier, giving researchers a stable platform to study quasiperiodic magnetism directly.
The study was published in the Journal of the American Chemical Society on July 7, 2026, with funding from the Japan Society for the Promotion of Science and the Japan Science and Technology Agency’s CREST program.
