Correlation between antiphase boundary defects and surface inhomogeneous properties in magnetite films

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04824
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 28030:Nanomaterials-related
• Research Institution: Hokkaido University
• Principal Investigator: SUBAGYO Agus 北海道大学, 情報科学研究院, 准教授 (30374599)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: マグネタイト / 走査型トンネル顕微鏡 / スピン計測 / 炭素吸着

Outline of Final Research Achievements

The low spin polarization of magnetite, a half-metallic material that has shown promise as a spintronics material, has been attributed to the formation of an antiphase domain boundary in the fabricated thin film. Using scanning tunneling microscopy, we have investigated the relationship between the atomic-scale structure of the antiphase domain boundary on the magnetite thin film surface and the surface spin polarization state, and have confirmed that the antiphase domain boundary leads to an inhomogeneous surface electronic state. To obtain high surface spin polarization, we have deposited carbon films on magnetite surface, and have observed the appearance of spin-polarized down-spin-derived electronic states by heated them at 400°C. We have developed an antiferromagnetic single-crystal Cr tip for imaging the surface spin-polarized states on an atomic scale and succeeded in fabricating a Cr single-crystal tip with good reproducibility.

Free Research Field

表面科学、低次元物質電子デバイス

Academic Significance and Societal Importance of the Research Achievements

本研究では、マグネタイトの低いスピン偏極度は、膜内に形成される逆位相境界による表面電子状態の不均一性に起因されることを確認した。また、マグネタイト上の炭素成膜はスピン偏極電子状態の出現をもたらしたことも確認した。さらに、原子スケールの表面スピン偏極電子状態取得のために単結晶のクロムスピンプローブを開発し、その性能と再現性が良好であることを確認した。ハーフメタル材料であるマグネタイトの低いスピン偏極の原因の究明とそのスピン偏極度回復方法の取得が、高スピン偏極材料の物性研究と高いスピン注入源材料開発にも重要な知見をもたらすため学術的・社会的意義のある成果である。