Magnetic skyrmions are topologically protected, nanoscale whirls of the spin configuration that tend to form hexagonally ordered arrays. As a topologically non-trivial structure, the nucleation and annihilation of the skyrmion, as well as the interaction between skyrmions, varies from conventional magnetic systems. Recent works have suggested that the ordering kinetics in these materials occur over millisecond or longer timescales, which is unusually slow for magnetic dynamics. The current work investigates the skyrmion ordering kinetics, particularly during lattice formation and destruction, using time-resolved small angle neutron scattering (TR-SANS). Evaluating the time-resolved structure and intensity of the neutron diffraction pattern reveals the evolving real-space structure of the skyrmion lattice and the timeframe of the formation. Measurements were performed on three prototypical skyrmion materials: MnSi, (Fe,Co)Si, and Cu₂OSeO₃. To probe lattice formation and destruction kinetics, the systems were prepared in the stable skyrmion state, and then a square-wave magnetic field modulation was applied. The measurements show that the skyrmions quickly form ordered domains, with a significant distribution in lattice parameters, which then converge to the final structure; the results confirm the slow kinetics, with formation times between 10 ms and 99 ms. Comparisons are made between the measured formation times and the fundamental material properties, suggesting the ordering temperature, saturation magnetization and magnetocrystalline anisotropy may be driving the timeframes. Micromagnetic simulations were also performed and support a scaling of the kinetics with sample volume, a behavior which is caused by the reconciling of misaligned domains.

中文翻译：

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用 TR-SANS 探测斯格明子晶格形成和破坏机制

磁性斯格明子是受拓扑保护的、自旋结构的纳米级漩涡，往往形成六边形有序阵列。作为一种拓扑结构，斯格明子的成核和湮灭以及斯格明子之间的相互作用与传统的磁系统不同。最近的研究表明，这些材料中的有序动力学发生在毫秒或更长的时间尺度内，这对于磁动力学来说异常缓慢。目前的工作使用时间分辨小角中子散射（TR-SANS）研究斯格明子有序动力学，特别是在晶格形成和破坏过程中。评估中子衍射图案的时间分辨结构和强度揭示了斯格明子晶格演化的实空间结构和形成的时间框架。对三种典型的斯格明子材料进行了测量：MnSi、(Fe,Co)Si 和 Cu ₂ OSeO ₃。为了探测晶格形成和破坏动力学，系统在稳定的斯格明子态下制备，然后应用方波磁场调制。测量结果表明，斯格明子快速形成有序域，晶格参数分布显着，然后收敛到最终结构；结果证实了缓慢的动力学，形成时间在 10 毫秒到 99 毫秒之间。对测量的形成时间和基本材料特性进行了比较，表明有序温度、饱和磁化强度和磁晶各向异性可能正在驱动时间范围。还进行了微磁模拟，并支持动力学随样品体积的缩放，这是由未对准域的协调引起的行为。