界面Dzyaloshinskii-Moriya相互作用下辐射状磁涡旋形成机制

辐射状磁涡旋结构是一种稳定的拓扑磁结构，因其具有热稳定性高、驱动电流小等特点，成为当前继斯格明子之后又一新兴的研究热点.本文利用微磁学模拟方法研究了在界面Dzyaloshinskii-Moriya相互作用（IDMI）下辐射状磁涡旋形成机制.结果表明：纳米盘直径越小，能稳定形成辐射状磁涡旋的IDMI强度范围就越大，当圆盘厚度增加一个数量级时，虽然可以稳定形成辐射状磁涡旋，但IDMI强度取值范围会随之变小.通过对不同磁矩初始态下辐射状磁涡旋的形成过程中磁矩、斯格明子数及各项能量变化的研究发现，环形涡旋和单畴均可作为辐射状磁涡旋形成的初始状态，但单畴初始态的形成时间比环形涡旋初始态的形成时间更长，其能量衰减时间比以环形涡旋为初始态的衰减时间更短.这表明形成辐射状磁涡旋极性比形成辐射旋性需要更长时间，且能量变化主要与涡旋核的生成及面内辐射状磁矩有关，而与涡旋核在盘中的位置无关.研究结果揭示了辐射状磁涡旋的形成机制，为基于辐射状磁涡旋的具体应用提供了理论依据.

Mechanism of magnetic radial vortex under effect of interfacial DzyaloshinskiiMoriya interaction

Recently, the topological magnetic textures, such as magnetic vortex, skyrmion, meron, have attracted wide attention. Siracusano et al. Siracusano G, Tomasello R, Giordano A, et al. 2016 Phys. Rev. Lett. 117 087204] found a new topological magnetic configuration, named a magnetic radial vortex. The magnetic radial vortex state is a stable topological magnetic texture. The magnetization in the center of the magnetic radial vortex, namely the radial vortex polarity, points upward or downward. The in-plane component of the magnetization, namely, the radial vortex radial chirality, orientates radially outward or inward. The magnetic radial vortex has become another emerging research hotspot after skyrmion, which can be attributed to its better thermal stability and lower driven current density. In this paper, we investigate the nucleation mechanism of magnetic radial vortex under the effect of interfacial Dzyaloshinskii-Moriya interaction (IDMI) by using the micromagnetic simulation. The results indicate that the smaller the diameter of the soft magnetic nanodisk, the more easily the wider range of the intensity of IDMI is created. When the thickness of the disk is increased by one order of magnitude, the magnetic radial vortex can be formed stably. Therefore, the intensity of IDMI can be further reduced by appropriately choosing the disc size. The magnetic radial vortex can be nucleated no matter whether the initial magnetization configuration is circular vortex or uniform state. However, if the initial state is uniform, the magnetization component along the z-axis direction is prerequisite. In the magnetic radial vortex nucleation process, the nucleation time of the uniform state is significantly longer than that of circular vortex, and the energy variation time of circular vortex is longer than that of the uniform state. In the process of the formation of magnetic radial vortex, the variation of magnetic moment, skyrmion number and energy are determined by different initial magnetization configurations. This work contributes to the understanding of the mechanism of magnetic radial vortex and provides a theoretical guideline for choosing reasonable disc size and IDMI strength. Moreover, the above-mentioned conclusions contribute to the practical applications of magnetic radial vortex in spin electric devices.