Defect Engineering and Mechanical Control for Atomic-scale Multiferroics via Lattice Defects

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03145
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Materials/Mechanics of materials
• Research Institution: Kyoto University
• Principal Investigator: Shimada Takahiro 京都大学, 工学研究科, 准教授 (20534259)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 格子欠陥 / 強誘電体 / 磁性 / マルチフィジックス特性 / 第一原理解析

Outline of Final Research Achievements

In this work, we aim to overcome the critical nano-dimensions where material functionality disappears and discover ultra-small magnetic ferroelectrics (multiferroics). We perform first-principles density-functional theory calculations to reveal the low-dimensional and atomic-scale ferroelectricity and magnetism appeared at lattice defects. The magnetic and ferroelectric properties localized to the defects are observed in the point defects, such as vacancies and anti-site defects, and in the line defects such as dislocation cores, and the single-atom scale multiferroics are successfully found. We also show that such lattice-defect properties can be controlled by external mechanical loading. Furthermore, by constructing a mechanics model to describe these lattice defect functions, we have succeeded in analyzing the phenomena of complex systems consisting of multiple lattice defects.

Free Research Field

計算材料力学

Academic Significance and Societal Importance of the Research Achievements

本研究は、臨界寸法以下の磁性・強誘電性は存在し難いという点を覆し、格子欠陥によって原子スケールの磁性強誘電体を見出した点や、機能と力学的変形の相互作用であるマルチフィジックス原理を解明し、力学特性-磁性-強誘電性の3異種物理特性が作用する力学を提案する点に学術的意義がある。特に、マルチフィジックス特性は、ひずみ負荷によるシリコンのバンドギャップの変化を利用する「ひずみシリコン」など、電子デバイスへの応用が始まりつつあり、本研究成果によって、より高度なナノデバイス設計や全く新しい技術・製品開発に繋がると考えられる。