Enhanced Phase Transition Properties in Fe3O4 Ultrathin Film Grown on Atomically Flat and Ordered Substrate

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K15116
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 28020:Nanostructural physics-related
• Research Institution: Osaka University
• Principal Investigator: Osaka Ai 大阪大学, 産業科学研究所, 特任助教(常勤) (70868299)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: 表面処理 / 完全結晶表面 / 強相関酸化物 / 相変化 / 欠陥

Outline of Final Research Achievements

Perfect surfaces can upgrade the quality of the films grown on them and ensure that their physical properties do not deteriorate. Here, an atomically flattened surface is homogeneously formed over an entire MgO(001) substrate by an original chemical polishing technique. The atomically flattened substrate enabled a nondeteriorating Verwey transition to be induced in a 50-nm-thick Fe3O4 thin film on the substrate owing to the extremely low defect density, which is 1/1000 of that of pristine MgO. Additionally, a statistical evaluation shows that the change in resistivity and the transition temperatures across Verwey transition shifts toward higher values. The result clearly shows the effectiveness of a substrate surface with both atomic flatness and high crystallinity in suppressing the variation of a characteristic among samples, leading to the development of high-performance magnetoresistive devices to manifest the materials’ potential physical properties.

Free Research Field

物性物理、酸化物エレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

本成果はあらゆる薄膜材料で材料本来の物性発現を可能にする方法論を明確に示しており、非常に波及効果が大きい。欠陥等の物性が不連続になる原因を排除することで、薄膜/基板界面の物理解明、結晶構造設計の統一的解釈が可能になり、界面物理、ナノ材料設計に関する議論を活性化させる。さらに物性劣化の無い機能性薄膜の実現はデバイスの機能向上、ナノレベルでのサイズダウンを可能にし、エネルギー問題解消に向けたBeyond Mooreを叶える大容量メモリ性能・超低消費電力スピントロニクスデバイスの開発を推進し、カーボンニュートラル社会の実現に大きく貢献する。