Moving state and its dynamics for the magnetic skyrmion at nonequilibrium steady and nonsteady states

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K03709
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Tohoku University
• Principal Investigator: Okuyama Daisuke 東北大学, 多元物質科学研究所, 助教 (30525390)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 非平衡状態の物理 / 中性子散乱 / 磁気スキルミオン

Outline of Final Research Achievements

In chiral magnet MnSi, it is known that the magnetic skyrmions start to move above the threshold current density jt ~ 1 MA/m2. To elucidate the moving and transient states induced by the change of the electric current flow, we study a small angle neutron diffraction experiment under an alternative electric current flow. In our study, the moving magnetic skyrmions keep a triangular lattice state and the magnetic skyrmion lattices near the sample edges move with plastic deformation, plastic flow. Furthermore, we found that for the plastic deformation of the magnetic skyrmion lattice, the few second relaxation time is necessary. In the plastic flow model, the dislocation of the magnetic skyrmion lattice moves with sliding on the magnetic domain wall of the skyrmion lattice. It is considered that the relaxation time is the time when the moving dislocation reaches the edge of the domain boundary from the other skyrmion lattice domain.

Free Research Field

磁性、固体物理

Academic Significance and Societal Importance of the Research Achievements

電流下で駆動中の磁気スキルミオンは三角格子を保ち試料端付近で塑性変形を起こしながら駆動する塑性流動を起こすことがわかっていたが、今回得られた研究結果より塑性変形を引き起こすには数秒の緩和時間が必要であることが判明した。これは磁気スキルミオンを高速、短時間で動かしている分には試料端付近のピニングの影響が小さいことを意味しており、磁気スキルミオンを使った記憶媒体などを実現するために必要不可欠な新しい知見を示した。