Investigation on electromagnon excitation of spin gap system by frequecny-sweep type ESR measurement

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05416
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Kobe University
• Principal Investigator: Sakurai Takahiro 神戸大学, 研究基盤センター, 助教 (60379477)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: スピンカレント

Outline of Final Research Achievements

We investigated the possibility that the origin of the direct transition from the singlet ground state to the excited triplet states which is observed in the spin gap system consisting of S = 1/2 antiferromagnetic spin dimer is the electromagnon excitation which comes from the spin current mechanism. We developed the frequency sweep type ESR system in THz region. The excitation from the singlet to the Sz = 0 state of the triplet states was successfully observed. Since this excitation is independent on the magnetic field and constant, only frequency sweep type ESR measurement can observe it. By taking the ESR selection rule of this system into account, we concluded that the observed excitation is the electromagnon coming from the spin current mechanism.

Free Research Field

電子スピン共鳴

Academic Significance and Societal Importance of the Research Achievements

エレクトロマグノンの平行モードの観測が、その識別手段として有効であることを示す事が出来た。ESRにおける直接遷移に関しては、Dzyaloshinsky-Moriya相互作用が存在する場合のESRの選択則については理論的に研究されてきたが、実験結果を満足に説明できるケースはむしろ例外的で、その統一的な理解には及んでいない。スピンカレント機構が直接遷移を許容にする一般則として加われば、ESR の選択則が非常に豊になってかつその研究が進む。更に、本研究でスピンギャップ系においてエレクトロマグノンが確認されれば、エレクトロマグノンの新しい探索対象を一気に広げると期待される。