Critical fluctuations in topological transitions of spin structures and their application to high efficiency thermoelectric conversion

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K13497
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: The University of Tokyo
• Principal Investigator: Kanazawa Naoya 東京大学, 大学院工学系研究科(工学部), 講師 (10734593)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Keywords: スキルミオン / ヘッジホッグ / トポロジカル相転移 / 小角中性子散乱 / キラル磁性体

Outline of Final Research Achievements

Many electron spins in a material behave as small magnets. These spins show various collective structures. When a spin structure with characteristic topological properties, such as skyrmion, is realized, there appears a huge electromagnetic response, which cannot be realized by classical electromagnetism. In this research, we developed chiral magnets and identified new topological spin structures called spin-hedgehog lattices. Those topological spin structures can be transformed into other structures by external stimuli such as a magnetic field and pressure. We also found giant Hall responses in association with the strong spin fluctuations upon the topological phase transition.

Free Research Field

物性物理

Academic Significance and Societal Importance of the Research Achievements

2009年にスキルミオンという新しいスピン構造が発見されて以降、様々なタイプのトポロジカルスピン構造が発見されてきました。それらはナノメートルスケールの磁気粒子として振舞うため、磁気記録メモリの性能を向上させる物質中の状態として注目を集めました。本研究では、トポロジカルスピン構造を磁場や圧力といった外部刺激によって自在に変形させることができ、その変形(トポロジカル相転移)に伴うスピンの強いゆらぎが電気伝導現象に大きな影響を与えるという新しい物理の側面を明らかにできました。