Spin-dependent quantum coherent phenomena in ferromagnet/layered superconductor hybrids

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K05244
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 29010:Applied physical properties-related
• Research Institution: Utsunomiya University
• Principal Investigator: Irie Akinobu 宇都宮大学, 工学部, 教授 (90241843)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 高温超伝導体 / スピントロニクス / 固有ジョセフソン接合 / ナノ構造 / 超伝導材料・素子 / 低温物性

Outline of Final Research Achievements

In this study, we fabricated ferromagnet/intrinsic Josephson junctions/ferromagnet structure and find the influence of spin current on intrinsic Josephson properties from both point of views of the interlayer coupling between intrinsic Josephson junctions and long-rang coupling over several junctions. In the magnetic field dependence of the critical current of the intrinsic Josephson junctions, it is shown that the critical current takes a local minimum when the magnetization of the upper and lower magnetic layers becomes antiparallel, and the spin current flows uniformly up to about 70 junctions. It was also shown that the observed magnetic field dependence of the critical current can be explained by a magnetic coupling model for the intrinsic Josephson junctions that considers the contribution of the induced magnetic field from ferromagnets and the influence of spin accumulation on Josephson coupling strength.

Free Research Field

超伝導電子工学

Academic Significance and Societal Importance of the Research Achievements

これまでの磁性体／超伝導体接合や磁性体バリアのジョセフソン接合，並びに磁性体／金属（半導体）接合におけるスピン輸送に関する研究は，高度な高品質薄膜作製技術を駆使して行われている。本研究では，高温超伝導体において原子層スケールで自己形成されたナノ超構造に着目することで，同構造に発現するジョセフソン効果とスピン流の巨視的量子現象の相互干渉を明らかにした。これは，スピン流に基づく物質の新機能性の探索に加え，高温超伝導体単結晶のスピントロニクス応用への可能性を示すものであり，高温動作が可能な超伝導エレクトロニクスの創出が期待できる。