Long-range magnetic order has been observed in quasicrystals, strange solids that show forbidden crystal symmetries, for the first time

Since the discovery of quasicrystals (QCs), solids that mimic crystals in their long-range order but lack periodicity, scientists have sought physical properties related to their peculiar structure. Now, an international group of researchers led by Tokyo University of Science, Japan, report for the first time a long-range magnetic order in QCs with icosahedral symmetry that turn ferromagnetic below certain temperatures. This groundbreaking discovery opens doors to future research on these exotic materials.

In 1984, a routine examination of an aluminum-manganese alloy revealed a curious anomaly that was previously thought to be crystallographically impossible－a five-fold rotational symmetry. This was the discovery (later recognized by Nobel Prize) of a "quasicrystal" (QC), a curious solid that shows long-range ordering similar to crystals but lacks their periodicity. Rather, the order is "quasiperiodic," which leads to some exotic symmetries absent in crystals. Ever since then, QCs have been the subject of enormous scientific interest.

But their potential applications remain uncertain since no physical property signifying their long-range quasiperiodic order, such as long-range magnetic order, has been observed. Until now, that is.

In a new study published in the Journal of the American Chemical Society, a global team of scientists led by Professor Ryuji Tamura of Tokyo University of Science (TUS), Japan, Professor Taku J. Sato of Tohoku University, Japan, and Professor Maxim Avdeev of the Australian Nuclear Science and Technology Organisation and University of Sydney, Australia, have reported the first-ever observation of long-range ferromagnetic order in icosahedral quasicrystals (i QCs or QCs with 5-fold rotational symmetry). Ms. Asuka Ishikawa and Dr. Shintaro Suzuki, members of the Tamura Laboratory at TUS, also made invaluable contributions to the project.

"This successful synthesis of ferromagnetic i QCs is the culmination of more than 10 years of research in our laboratory," says Prof. Tamura, "Nobody knows what kind of peculiar behavior they will further reveal or how they can be exploited for the advancement of technology, but now we have finally taken the first step. Elucidating the properties of these ferromagnetic QCs will contribute greatly to the development of science."

There are four major types of magnetic order: ferromagnetism, antiferromagnetism, paramagnetism, and diamagnetism. The discovery of antiferromagnetic and ferromagnetic transitions in approximant crystals (APs)－crystals with a somewhat similar structure to the related QCs that can be studied using conventional techniques－inspired the research group to look for magnetically ordered i QCs. For their research, the team prepared alloys of gold (Au), gallium (Ga) and gadolinium (Gd) and gold, gallium, and terbium (Tb). Using conventional X-ray diffraction, they observed the formation of an icosahedral quasicrystal phase for both Au-Ga-Gd and Au-Ga-Tb.

They then investigated the properties of the two i QCs using magnetic susceptibility and specific heat measurements. They found that both alloys showed a ferromagnetic phase transition at 23 K (Gd i QC) and 16 K (Tb i QC), a signature of long-range magnetic order. To further validate these results, they performed neutron diffraction experiments using ECHIDNA (ANSTO, Australia) and ISSP-GPTAS (JRR-3, Japan), and looked at the neutron diffraction patterns of the i QCs at different temperatures. They observed prominent Bragg peaks below their respective transition temperatures, confirming the ferromagnetic nature of the i QCs.

Attempts to synthesize magnetic i QCs until now have all ended in "spin-glass-like freezing," characterized by a disordered magnetic state. Against this backdrop, the discovery of long-range ferromagnetic order in this study has consequences far beyond the landscape of the physical properties of materials and opens doors to tailored magnetic materials. "The crystal symmetry of ferromagnetic QCs is much higher than that of conventional periodic crystals, which makes it possible to apply them as ultrasoft magnetic materials," says Prof. Tamura.

With the decades-long quest for long-range magnetic order in i QCs finally at an end, the world is now eagerly waiting to see what this groundbreaking discovery entails. With such superlative research pioneering the way, it won't be long before we find out!

Reference

Authors	:	Ryuji Tamura1, Asuka Ishikawa2, Shintaro Suzuki1, Akihiro Kotajima1, Yujiro Tanaka1, Takehito Seki3, Naoya Shibata3, Tsunetomo Yamada4, Takenori Fujii5, Chin-Wei Wang6, Maxim Avdeev7,8, Kazuhiro Nawa9, Daisuke Okuyama9, and Taku J. Sato9
Title of original paper	:	Experimental observation of long-range magnetic order in icosahedral quasicrystals
Journal	:	Journal of the American Chemical Society
DOI	:	10.1021/jacs.1c09954
Affiliations	:	1Department of Materials Science and Technology, Tokyo University of Science, 2Research Institute for Science and Technology, Tokyo University of Science, 3Institute of Engineering Innovation, School of Engineering, The University of Tokyo, 4Department of Applied Physics, Tokyo University of Science, 5Cryogenic Research Center, The University of Tokyo, 6National Synchrotron Radiation Research Center, 7Australian Nuclear Science and Technology Organisation, 8School of Chemistry, The University of Sydney, 9Institute of Multidisciplinary Research for Advanced Materials, Tohoku University.

Latest Article Publication Date: November 17, 2021
Method of Research: Experimental study
Subject of Research: Not Applicable
Conflict of Interest Statement: None

Further Information

Professor Ryuji Tamura
Department of Materials Science and Technology,
Tokyo University of Science
Email: tamura【@】rs.tus.ac.jp

Professor Taku J. Sato
Institute of Multidisciplinary Research for Advanced Materials
Tohoku University
Email: taku【@】tohoku.ac.jp

Professor Maxim Avdeev
Australian Nuclear Science and Technology Organisation
Email: max【@】ansto.gov.au

Media contact

Tsutomu Shimizu
Public Relations Divisions
Tokyo University of Science
Email: mediaoffice【@】admin.tus.ac.jp
Website: https://www.tus.ac.jp/en/mediarelations/

Institute of Multidisciplinary Research for Advanced Materials
Tohoku University
Email: press.tagen【@】grp.tohoku.ac.jp

Phil McCall
Australian Public Affairs
Australian Nuclear Science and Technology Organisation (ANSTO)
E-mail: pmccall【@】ansto.gov.au

About The Tokyo University of Science

Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of "Creating science and technology for the harmonious development of nature, human beings, and society", TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.