Composition- and structure-controls and search for magnetic properties of eutectoid-decomposition-type metal/oxide nanocomposites

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K05079
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: Ehime University
• Principal Investigator: Yamamuro Saeki 愛媛大学, 理工学研究科(工学系), 准教授 (10402653)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 共析分解 / 鉄 / スピネルフェライト / ナノコンポジット / 磁性 / 磁石

Outline of Final Research Achievements

Magnetic nanocomposites consisting of a ferromagnetic alloy (Fe-Co alloy) and a ferrimagnetic iron oxide (spinel ferrite) have been prepared by eutectoid decomposition of cobalt-substituted iron oxide with FeO crystal structure. Controls of their composition and microstructure in the nanoscale and magnetic properties were investigated. It was found that the cobalt-substitution led to a large shift in the formation of the FeO phase and the eutectoid decomposition to the high-temperature side. After the decomposition, cobalt was distributed into the magnetic alloy and the magnetic iron oxide phases, forming cobalt-ferrite-based nanocomposites with a high saturation magnetization exceeding that of cobalt ferrite alone. It was also found that cobalt was preferentially distributed to the magnetic alloy. In addition, the co-substitution of cobalt and copper was confirmed to slightly promote the decomposition of the cobalt-substituted FeO phase.

Free Research Field

工学、ナノ材料学

Academic Significance and Societal Importance of the Research Achievements

Fe2+イオンの一部をCo2+イオンで置換したFeO相の共析分解という冶金学的手法により、結晶磁気異方性の大きなCoフェライトを主相とした磁性ナノコンポジットを形成可能なことを示した。そして、Co置換が共析分解後における形成相の組成・磁気特性に及ぼす影響について明らかにした。以上の結果は、磁性合金とスピネルフェライト相の組み合わせを自在に選択できる可能性を示している。スピネルフェライトは構成金属イオンを異種金属イオンで置換することにより磁気特性を多彩に制御できることから、各種スピネルフェライトとFe基合金からなるナノコンポジット作製の新たな手法を提示することができた。