Strain engineering for the development of a ferromagnetic europium compound and emergence of giant magnetic anisotropy

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05227
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 36010:Inorganic compounds and inorganic materials chemistry-related
• Research Institution: Kyoto University
• Principal Investigator: Takatsu Hiroshi 京都大学, 工学研究科, 准教授 (60585602)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: EuVO2H / 磁気異方性 / 応力 / トポケミカル反応 / XAS / XMCD / 薄膜合成 / 高圧実験

Outline of Final Research Achievements

We have investigated the magnetic properties of EuVO2H, a europium-based ferromagnet with an anion-ordered structure of alternating VO2 and EuH layers, displaying significant perpendicular magnetic anisotropy (PMA). Our research included synthesizing various thin films, conducting magnetization, X-ray absorption spectroscopy, X-ray magnetic circular dichroism, photoelectron spectroscopy, and high-pressure powder experiments. We found that inter-site charge transfer (ICT) between Eu2+ and V3+, influenced by strain and pressure, is key for PMA in EuVO2H. Exploiting this ICT, we enabled carrier control by substituting Eu2+ with iso-valent elements like Sr2+, manipulating the challenging 3d and 4f bands in oxide perovskites. Our approach uses topochemical reactions, assisted by substrate strain and external stimuli, which paves the way for developing new functional materials with unique structures and properties.

Free Research Field

物性物理学、無機固体化学

Academic Significance and Societal Importance of the Research Achievements

ユウロピウム化合物では磁性を担うEu2+の軌道角運動量がゼロ（L = 0）であるため、これまで、磁気異方性を示さないことが一般的であった。本研究の遂行によりEuVO2Hの巨大な垂直磁気異方性の発現メカニズムが明らかになったことは、磁性研究の新しい一面を拓くことにつながるため、学術的に重要な成果である。ここで得られた知見、すなわち、サイト間の電荷移動を通じた磁気異方性の増強やキャリア制御により、レアエレメントからの脱却など、人類の持続性確保に貢献する機能性材料の開発へつなげていくことが期待できるため、社会的にも意義が深い研究と考えられる。