Quasicrystals (QCs) feature odd structures and fascinating atomic configurations. On the surface, they resemble crystals, but at the atomic scale, they are organised but lack periodicity. Such structural configurations endow quasicrystals with symmetry and other unique qualities that crystals lack. Icosahedral QCs (i QCs), which have a unique geometric structure, in particular, exhibit intriguing magnetic properties.
Recently, a research team from the Tokyo University of Science (TUS) lead by Professor Ryuji Tamura found ferromagnetic order in gold-gallium-gadolinium and gold-gallium-terbium i QCs. However, because they also included a significant amount of the approximant crystal (AC) phase, these I QCs were not suitable for further research on ferromagnetism in I QCs.
Despite sharing a structure with QCs, ACs are also magnetic, which makes it difficult to conduct research on the magnetism of the QC phase alone.
Professor Tamura’s group has now created a brand-new gold-gallium-dysprosium (Au-Ga-Dy) i QC to fill this gap. Professor Tamura claims that “The Au-Ga-Dy i QC is ferromagnetic, highly tunable, and has high phase purity.”
Physical Review Letters is where the research team, which also included Mr. Ryo Takeuchi and Dr. Farid Labib from TUS, published its findings. The editors have chosen this paper as their suggestion.
Utilising mother alloys that contained 15% Dy, 62–68% Au, and 23–17% Ga, the new i QCs were created. Rapid quenching was used after arc melting to create the mother alloys. Powder X-ray diffraction, electron microscopy, electron diffraction, and magnetic susceptibility measurements were used to study the resulting i QCs.
The scientists discovered that the artificially created i QC was polycrystalline and had a very pure ferromagnetic phase. They were also able to explain how the ferromagnetic transition resembles a mean-field.
Additionally, the researchers found that the new i QCs exhibit a maximum Weiss temperature, a crucial element in the ferromagnetic transition, at an electrons-per-atom (e/a) ratio of 1.70, which is consistent with earlier results for ACs. This finding proves that the Weiss temperature and e/a ratio, a parameter that shows changes in the i QC’s Fermi energy, may be used to fine-tune the magnetic characteristics of i QCs.
These results also show that the presence of exotic magnetic orders and the balance of ferromagnetic and antiferromagnetic interactions may be changed in i QCs by changing the Fermi energy or the e/a ratio.
“The discovery of pure tunable ferromagnetic quasicrystals has the potential to revolutionize and expand the academic system based on crystals. Applying our findings to current theoretical work in the field, for example, in the realm of non-coplanar spin configurations such as hedgehog and whirling configurations, can lead to various nontrivial physical properties in i QCs, including anomalous and topological Hall effects,” concludes Prof. Tamura.
These discoveries accelerate the development of technologies like magnetic data storage, spintronics, and magnetic sensors and open up new horizons for magnetic materials.
