Anomalous Magnetism in Quasicrystals and Approximants

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K18764
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics and related fields
• Research Institution: Tokyo University of Science
• Principal Investigator: Tohyama Takami 東京理科大学, 理学部第一部応用物理学科, 教授 (70237056)
• Co-Investigator(Kenkyū-buntansha): 杉本 貴則 東京理科大学, 理学部第一部応用物理学科, 助教 (70735662)
• Research Collaborator: Tamura Ryuji
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: 準結晶 / 近似結晶 / スピンアイス / 磁気モノポール

Outline of Final Research Achievements

This study reveals novel physical properties and their characteristics derived from the magnetic order in the approximant of quasicrystals containing rare earth ions. The approximant forms an octahedral lattice where rare earth ions located at the apex position of the icosahedron are shared, and there is a possibility that an octahedral spin-ice state can be obtained. First, we found that the characteristics of the model that includes the anisotropy of the direction of localized spin together with itinerant the magnetism agree well with the existing experiment. Secondly, we found that monopole excitation by spin ice propagates, considering the terms derived from spin-orbit interaction and ferromagnetic interaction. Thirdly, we obtained theoretical results on the quantum criticality of the phase transition among spin glass, ferromagnetic, and antiferromagnetic phases, as well as magnetic fluctuation and defects.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

近似結晶の実験で得られている基底状態の格子定数依存性を理論計算によって再現できたのは、この物質系を支配している重要な相互作用を明らかにしたことに対応しており、今後のこの系の基底状態の研究の指針となる成果といえる。また、この系にスピンアイスの特徴が出現する条件を明らかにしたことは、今後の実験に対する指針を与えたことになり、今後のこの系の研究の発展に大きく寄与しているといえる。