Study on magnetism of ultra-thin films of 4d transition metals by using spin-polarized scanning tunneling microscopy observation

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K05316
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Hokkaido University
• Principal Investigator: MATSUYAMA Hideo 北海道大学, 理学研究院, 特任准教授 (50374187)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: スピン / Pd / 超薄膜 / 量子井戸

Outline of Final Research Achievements

Although Pd is a non-magnetic material, it has been reported that ferromagnetism occurs in ultra-thin Pd films on STO(001) material. However, there are no reports directly observing the spin distribution of Pd thin films. Initially, we planned to deposit ultra-thin Pd films on STO, but although we tried deposition under various conditions, we were unable to obtain a Pd epitaxial film. Therefore, we deposited ultra-thin Pd films on a Cu(001) substrate and observed differential conductance dI/dV images of the Pd film by using spin-polarized STM with antiferromagnetic Cr tip at room temperature. We obtained bright and dark contrast within the flat terrace of the obtained dI/dV image. It can be interpreted as a spin contrast of a magnetic thin film with a multi-domain structure, but more experimental data will be needed to conclude that Pd exhibits ferromagnetism.

Free Research Field

表面磁性

Academic Significance and Societal Importance of the Research Achievements

慶應大のグループはSTO(001)基板上にPd超薄膜を成膜し、基板を含めた試料の磁化測定からある特定の膜厚でPdに強磁性が発現すると結論付けた。しかし、試料には大きな常磁性成分があり、また磁性不純物も混入する可能性があるため、Pd超薄膜のスピン分布を直接観察することが望まれていた。STO基板上に原子レベルで平坦なPd超薄膜を成膜することはできなかったが、Cu(001)基板上に形成することに成功し、スピン偏極STMでPd薄膜を観察し、スピンに依存すると考えられるコントラストを得た。Pd薄膜が強磁性を発現したと結論付けることはまだできないが、データの蓄積を進めることで結論を導くことが可能である。