Observation of AFM spin fluctuations in iron-based highest-Tc superconductor

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13499
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Soshi Iimura 東京工業大学, 元素戦略研究センター, 特定講師 (80717934)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 鉄系超伝導体 / 磁気散乱 / 中性子 / ヒドリドイオン

Outline of Final Research Achievements

In this study, the spin dynamics in electron-doepd high-Tc 1111-type iron-based superconductors, REFeAsO1－xDx, have been investigated by using inelastic neutron scattering(INS). It is revealed that the spin excitation in the AFM phase at x = 0.5 is gapless and it may originate from quasimagnetic isotropy within the Fe-ab plane. Moreover, the stronger magnetic excitations at x = 0.5 than those at x = 0 is observed and survive even at much higher temperature than the Neel temperature. In addition, it is also found that a slightly electrond REFeAsO1－xHx phase with a smaller RE has an intrinsic instability and a heavy electron-doping can stabilize this phase.

Free Research Field

固体化学

Academic Significance and Societal Importance of the Research Achievements

本研究によってREFeAsO1-xDx(RE = 希土類元素)中のスピンの動的挙動が明らかとなった．超伝導発現下における動的スピンの観測を通した超伝導機構の解明まで至ることが出来なかったが，高濃度電子ドープ1111型鉄系超伝導体中のスピンダイナミクスはこの系ならではの電子状態を反映していることが分かった．これらの結果は本系が鉄系中でもより電子相関が強く，スピンが局在した部類に入ることを示している．また，小さい希土類元素を置換した1111系の相安定性に関する知見はこれら高Tc系のさらなる物性解明に向けた試料調製にインサイトを与える結果となっている．