Novel magnetic properties of two-dimensional ferromagnetic van der Waals atomic layers

2022 Fiscal Year Final Research Report

• Project/Area Number: 18H03877
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 29:Applied condensed matter physics and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Hirahara Toru 東京工業大学, 理学院, 教授 (30451818)
• Co-Investigator(Kenkyū-buntansha): 秋山 了太 東京大学, 大学院理学系研究科(理学部), 助教 (40633962)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 磁性トポロジカル絶縁体ヘテロ構造 / 二次元磁性体

Outline of Final Research Achievements

In this study, we have aimed to develop a new ferromagnetic 2D v-DW atomic layer material and investigated its physical properties from various aspects to elucidate the origin of its magnetization properties. As a result, we succeeded in developing a new 2D v-DW magnetic material, Mn4Bi2Te7, and clarified that the relationship between the magnetization properties and the band structure of the surface Dirac electrons cannot be explained by conventional theories. Furthermore, in the sandwich structure of MnBi2Se4/Bi2Se3, the magnetic interaction between neighboring magnetic atoms and its mediation by the nonmagnetic element Se were demonstrated for the first time. Regarding the controversial magnetization properties of VSe2, it was clarified that VSe2 is not ferromagnetic even at low temperatures, but exhibits short-range order and antiferromagnetic behavior.

Free Research Field

物性実験(量子表面界面ナノ物理)

Academic Significance and Societal Importance of the Research Achievements

本研究によってこれまで極低温にとどまっていたトポロジカル物性と磁性の協奏現象である量子異常ホール効果を高温にする方法が示され、実際に2021年に7 Kという液体ヘリウム冷却で到達可能な温度で実現された。さらに本研究の成果によって表面ディラック電子のバンド構造と磁化特性の関係が従来の理論的な枠組みでは説明されず、新たな理論の構築が必要なことが明らかになった。これらは新しい二次元磁性体の開拓および、そのトポロジカル物性との協奏で予想されている新奇な電気磁気効果の実現に向けて重要な知見である。