We report an experimental study of the emergence of nontrivial topological winding and long-range order across the paramagnetic-to-skyrmion lattice transition in the transition metal helimagnet MnSi. Combining measurements of the susceptibility with small-angle neutron scattering, neutron-resonance spin-echo spectroscopy, and all-electrical microwave spectroscopy, we find evidence of skyrmion textures in the paramagnetic state exceeding ${10}^3\AA$, with lifetimes above several ${10}^{-9}\mathrm{s}$. Our experimental findings establish that the paramagnetic-to-skyrmion lattice transition in MnSi is well described by the Landau soft-mode mechanism of weak crystallization, originally proposed in the context of the liquid-to-crystal transition. As a key aspect of this theoretical model, the modulation vectors of periodic small-amplitude components of the magnetization form triangles that add to zero. In excellent agreement with our experimental findings, these triangles of the modulation vectors entail the presence of the nontrivial topological winding of skyrmions already in the paramagnetic state of MnSi when approaching the skyrmion lattice transition.

中文翻译：

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MnSi中起伏的Skyrmion纹理的弱结晶

我们报告了对过渡金属直升机磁铁MnSi中顺磁至Skyrmion晶格过渡的非平凡拓扑绕组和远距离有序出现的实验研究。将磁化率的测量与小角度中子散射，中子共振自旋回波光谱和全电微波光谱相结合，我们发现顺磁性状态下的天rm素织构超过了${10}^3\mathrm{一种}$，使用寿命超过几个 ${10}^{-9}\mathrm{s}$。我们的实验结果表明，MnSi中的顺磁至Skyrmion晶格跃迁可以通过弱结晶的Landau软模机制很好地描述，该机制最初是在液相至晶体跃迁的背景下提出的。作为该理论模型的关键方面，磁化强度的周期性小振幅分量的调制矢量形成加零的三角形。与我们的实验结果非常吻合，调制矢量的这些三角形意味着，在接近天体离子晶格转变时，已经处于MnSi顺磁性状态的天体离子的非平凡拓扑缠绕的存在。