Fabrication of Transparent Amorphous Oxide Semiconductors with Magnetic Ordered Structure

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K19021
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 36:Inorganic materials chemistry, energy-related chemistry, and related fields
• Research Institution: University of Yamanashi
• Principal Investigator: Yanagi Hiroshi 山梨大学, 大学院総合研究部, 教授 (30361794)
• Project Period (FY): 2021-07-09 – 2024-03-31
• Keywords: アモルファス酸化物半導体 / 巨大磁気抵抗

Outline of Final Research Achievements

In this study, the magnetoresistance (MR) of the amorphous In-M-O system (M: transition metal element) was investigated. The Hall and Seebeck coefficients at RT for the samples showing conductivity were both negative, indicating that the obtained samples exhibit n-type conduction. The carrier concentrations of the obtained samples were generally between ~10^19 and 10^20 cm-3. For the M = Ni samples, thin films with Ni concentrations of 4-6% and carrier concentrations of 10^20 cm-3 exhibited negative MR. On the other hand, all 10^19 cm-3 films showed positive giant MR below 20 K, with a maximum of 100% at 5 K for the 7% film. The 10^19 cm-3 films were found to be dominated by VRH conduction at low temperatures. However, this alone cannot explain the origin of the giant MR observed in this study. The localized spins and the presence of d-electrons originating from the amorphous structure may contribute to the positive giant MR at low temperatures.

Free Research Field

無機材料科学

Academic Significance and Societal Importance of the Research Achievements

アモルファス酸化物半導体において、１００％を超える巨大磁気抵抗を初めて観察した。この巨大磁気抵抗の発現には磁性元素の濃度だけでなく、キャリア濃度や伝導機構が影響していることを明らかにしたが、巨大磁気抵抗の起源の解明はまだ途上にある。さらなる研究の深化により巨大磁気抵抗の起源が明らかになれば、磁気抵抗を示す温度や大きさの制御につながる可能性がある。特に、室温で実現できれば、実用的な磁気抵抗素子への応用などが期待される。